Certainly not, but there are a lot of issues here that must be dealt with.

The first is what constitutes a biography, and perhaps more importantly what exactly the de bello Gallico and de bello civili are as texts. Neither is an idle question. The BG and BC are called in our manuscripts "commentarii," and Cicero refers to them by the same term. A commentarius was, in its origin, a record, initially priestly, of acta (roughly "records") conducted by a particular body, whether official ones like magistrates or voluntary ones like collegia. A commentarius was therefore, conceptually, one part of a series, which compiled together made a whole, the commentarii. By the first century the term appears to have become a synonym for Greek ὑπόμνημα, a "memory aid." Cicero refers to notes and drafts of speeches as commentarii. Yet at the same time commentarii were clearly not necessarily official records or rough notes, they could also be polished literary works. The problem is that Caesar's commentarii are our sole extant example of the form. The only other example we have is the commentariolum petitionis, lit. the "little commentarius of electoral campaigning," which is quite short and can only be described as a handbook, though it is likewise a clearly very polished work.

In form, then, we're unclear on how Caesar fits into the literary milieu of his time. Biography is really a form of later classical literature, especially in Greek, and neither Caesar nor his predecessors is properly biography. But how much Caesar differed from his contemporaries and predecessors is a matter of massive debate, with very little evidence. Further, it's not clear what the point of the BG and BC is. Cicero in the Brutus described Caesar's commentarii as notes written as source material for a historian to write about his campaigns. That no such history materialized in Caesar's lifetime Cicero attributes to the fact that they were so highly polished and well put together that they were good enough to stand on their own, which sounds like recusatio. Cicero similarly mentions in a letter that he has written up commentarii as notes for a poem or history of his own consulship in 63 that he is interested in commissioning--nobody ended up accepting the commission, so Cicero wrote the poem himself. Cicero therefore is an obvious predecessor to Caesar, and it's worth noting that while the poem was much maligned, it was not for the project of writing an epic about a living man's (the author's himself) consulship, but because Cicero was not a very good verse writer and the poetry wasn't very good. There seems to have been no significant problem with writing (tasteful) panegyric of one's own deeds in the first century, and in fact during Cicero's attempts to commission the poem he was actually told to write it himself. Another obvious predecessor is Sulla. Plutarch tells us that Sulla wrote ὑπομνήματα apparently in several books (he mentions a passage from the tenth book), to which he refers pretty frequently. These are typically assumed to be commentarii of some type, but we don't really know what form they took since they don't survive, though Plutarch and probably Appian used them as a source. A typical conjecture, which we have decent reason to think is correct, is that commentarii of similar type were quite common, though there is little evidence and Caesar's and Sulla's appear to have stood out in particular.

The final problem is that of propaganda. In order to demonstrate propaganda you need to demonstrate what Caesar's purpose was, and to do that you need to be able to show how the text was published. The trouble is that we have no idea. There's zero evidence for the publication of the text, except what comes in the text itself and our knowledge that since Cicero refer to the commentarii in the Brutus the BG at least must have had some form already in 46. But the BG could not have taken its final form before 50 or 51, because it refers to events that occurred in that year. And then there's the problem of how the BG fits into the BC, whether it's looking ahead to the BC or not (which should probably push the date of its final form even later). We don't know the audience of the BG and BC, scholars have argued for a senatorial audience, a popular audience (unlikely in the extreme, in my opinion), or that there was no audience, because of the way that commentarii were essentially source material and since Tacitus in the Dialogus says that Caesar distributed his poems privately to his friends (a not uncommon method of publication), which might suggest that the commentarii also were not intended to be published at all. We don't have anybody who talks about it, and we don't have anybody who even talks about the purpose of Caesar's text, even though we know that Caesar wrote polemics (the Anticatones).

In any case Caesar was not the first biography, in that he is not a biography, nor was he the first text of his kind, at least broadly if not specifically, since we do not have enough information to say anything about the form of earlier commentarii and similar literature. Further, he was not the first text of this kind to be written "with political intent"--a feature of many commentarii seems to be precisely that they are political texts, over and out. And indeed, this sort of political-historical text goes back to the very earliest literature. Cato's prose is somewhat similar, with a very deliberate political bent running underneath it. And Ennius' epic is clearly a historical-political epic, and is quite overtly presented as one, they're called Annals for Christ's sake. Nor is the recent nature of his subject any great obstacle. Cicero's epic poem was published by 60 at the latest, only three years after his consulship, much closer to the events than the earliest books in the BG were to the date of the final edition, if whatever the BG was published as can be properly called an edition. Whether Caesar is truly different is hard to judge. We don't have the evidence, we don't have the texts. We cannot determine whether other contemporary texts of this kind were like Caesar. Cicero in the Brutus seems to imply that Caesar's text was more rhetorically developed, more polished, and more literary than most similar commentarii, and while Caesar's Latin is trivially easy it's extremely rhetorically dense and an impressive piece of prose literature, made perhaps even more impressive by our problems contextualizing it, which lead to many difficulties in interpretation and understanding the text. But Cicero doesn't say that outright, and the passages from Sulla's ὑπομνήματα that Plutarch either quotes or more likely paraphrases seem to be similarly literary, and Plutarch seems to suggest that the ὑπομνήματα were an apologia of Sulla, which would suggest that they were highly rhetorical and very polished.