(Some quick notes on terminology: Firstly, Zungar, Zunghar, Dzungar, Dzungar and Junghar are all acceptable variant spellings; I have opted for Zunghar out of familiarity. Secondly, the term 'bondservant', which crops up in a quote later, refers to a particular category of enslaved person known in Manchu as booi.)

The post you've come across is problematic for a number of reasons, and while I do have specific criticisms I want to first lay out a general statement about the Zunghar Genocide to begin with so as not to broadcast those problematic elements before frontending what I would consider to be the most historiographically correct narative.

I've written about the Zunghar Genocide before in this answer, which as you will note is more about the context than the act. The reason for that is relatively simple: almost the entire historiography of the Zunghar Genocide in English consists of a few pages in Peter Perdue's 2005 monograph China Marches West. This makes discussing the event in depth difficult, especially as many of the details of the genocide given in Perdue's work, particularly on its demographic impact, derive primarily from Wei Yuan's Shengwuji, a privately-written military history of the Qing composed over 80 years later by a Cantonese scholar, Wei Yuan.

Even if we accept the not-unlikely scenario that Wei Yuan's figures were very rough estimates, we still have to acknowledge the sheer scale of the mortality suffered by the Zunghars in 1757-8. Per Perdue's summary of Wei Yuan, the Zunghar population was numbered by the Qing at around 600,000, of whom 30% were killed directly by the Qing army and 40% died of smallpox (against which Qing troops were mostly inoculated). Of the survivors, two-thirds fled to the Kazakh hordes or became Russian clients, while the remainder were enslaved by the Qing. Even if a 70% death rate were considered exaggerated, whatever actual, somewhat smaller figure it might be would still be horrifically vast.

The thing to bear in mind is that genocide is defined by intent, not by extent. There is no point on the number line dividing genocide from some lesser form of systematic mass killing, because the distinguishing feature of genocide is not quantitative but qualitative: it is the targeted killing of members of one or more groups of people who are defined as having a certain identity, on the basis of said identity. This is why there is the related category of cultural genocide, in which a state or polity attempts to erase a particular identity without aiming to actually kill those who are deemed to fall under that identity. To state it in brief, genocide is an attempt to destroy an identity, typically through the intentional killing, by direct or indirect action, of those the perpetrator categorises under that identity.

And with that in mind, the Zunghar Genocide absolutely, unequivocally counts as an undertaking with genocidal intent. If we quote Perdue verbatim here:

...Qianlong rejected all leniency. He now ordered the massacre of all Zungharian captives: “Show no mercy at all to these rebels. Only the old and weak should be saved. Our previous military campaigns were too lenient. If we act as before, our troops will withdraw, and further trouble will occur.” In another edict he declared: “If a rebel is captured and his followers wish to surrender, he must personally come to the garrison, prostrate himself before the commander, and request surrender. If he only sends someone to request submission, it is undoubtedly a trick. Tell Tsengünjav to massacre these crafty Zunghars. Do not believe what they say.”

He clearly had to overcome resistance from local military commanders, since he repeated his order several times, using the term jiao (extermination) over and over again. General Jaohûi was praised and awarded high rank for reporting massacres, as was Tangkelu, who captured the Khoit Chebudeng Dorji and “exterminated his followers.” Tangkelu was allowed to incorporate his enemy’s families and cattle into his own tribe. Other commanders, like Hadaha and Agui, however, were punished for merely occupying Zunghar pastures while allowing the people to escape. The remnants of Amursana’s shattered bands were to be tracked down even into Russian territory and eliminated.

The emperor deliberately targeted young and able men in order to destroy the Zunghars as a people. When Chebudengzhabu captured a group of Khoits, whom he was going to award to the loyal Khalkhas, the emperor instructed him to “take the young and strong and massacre them,” and award only the women as booty. Even some Zunghar youths who surrendered after the defeat of their elders could not be spared, since “their ancestors had been chieftains.” They had to be executed or made bondservants of the conquering soldiers. In 1756 the court had recommended the use of food relief to win over the Zunghar people by giving them grain, tea, and animals if they surrendered. Now the emperor implicitly recommended the use of starvation tactics, commenting that it would be “easy to exterminate rebels because they had run out of provisions.” Old men, children, and women were to be spared and sent as bondservants to other Mongol tribes and Manchu bannermen, but they would lose their tribal identity; they could not preserve their tribal (otoq) names or their titles, such as zaisang (minister or clan leader). Reliable Mongols designated to supervise these remnants took instead the Chinese official titles zongguan and fuzongguan.

The intent and execution of the acts here are clear: the Qianlong Emperor was ordering the complete and total extermination of the Zunghars as a people. That is not to say that he was seeking the death of every individual Zunghar. Rather, the aim was to destroy Zunghar family and tribal units in order to erase the idea of the Zunghars existing as a coherent group of people. Yes, many Zunghar individuals survived. Indeed, a handful who defected to the Qing before the genocide, such as Ayusi, actually attained high status within the Qing state, but they did so through swearing new loyalties and participating in the slaughter of their former fellow-tribespeople. And there were those enslaved and those who fled among the Russians and Kazakhs. But most of those who did so took on new tribal identities. Aside from a few pockets of self-identifying Olots (one of the Zunghar sub-tribes), the Zunghars as a people were utterly wiped out.

I will address specific issues with the post in a reply to this answer later.