Of course the answer is going to be "it depends" but what I'm asking is a bit more specific than that.
In general, modern academic historians seem to focus a lot on social history these days. So if you have an academic historian writing about baseball you're going to get a lot of analysis of the role that baseball has played in society and not much about how the game was played, developments in coaching and training, etc.
That's all well and good but how often does this focus on social history extend so far that you get historians writing about a subject they know nothing about? The reason I'm asking this is that there's only one technical subject that I know a lot about: brewing. I love homebrewing and I've read a lot about historical brewing techniques in different parts of the world.
So when I listened to some history podcasts and the podcasters had interviews with academic historians who had written a lot about historical brewing I was very excited to listen to them. And then I was completely gobsmacked. One of the historians had done archeological work on beer pots and was able to look at the residue and trace where and when and where people used malted vs. unmalted grain which was great and very informative. The other two did economic analysis by measuring beer jars and social history by looking at the records of brewers guilds. The economic and social analysis seemed mostly solid but it was obvious that they had very little knowledge about brewing. For example getting basic information about the impact of hops completely backwards or wildly exaggerating how long it takes for fermentation to produce an appreciable amount of alcohol. Not small errors and ones that would've been easy to correct with even a minor amount of study of the brewing process. And no, this isn't the sort of error that could be chalked up to changes in the brewing process over the centuries. And then they based some of their conclusions on their misconceptions of the basics of brewing. And the beer wasn't a side issue either, one of these historians had written an entire book about historical brewing.
This made me worried since I know very little about historical ceramics production, agricultural techniques, metallurgy, construction, etc. etc. so if I read something about one of those subjects by an academic historian who doesn't understand the technical dimensions of those subjects then I have no way of being able to tell if they're feeding me errors or not.
So, when historians talk about the specifics of how people did stuff in the past how must salt should I take that with? Are there lots of historians out there writing about agriculture without knowing the difference between wheat and barley? Is it common for historians to write a lot about the social impact of things that they know nothing about or it just an anomaly that I've run across a couple historians who write about the only technical subject I'm proficient in that are making obvious errors?
This is where good history emphasises interdisciplinary knowledge. For example, historians may consult experts in modern counterpart tools when attempting to understand tools of the past. Various memes and clickbait articles have gone about with something like "historians were BAFFLED by (historical object) until (modern-day experts) showed them it was really for THIS" and usually the person who asked the modern-day expert was a historian. Medical experts may also be consulted on medical issues, for example, in the paper "The nature of King James VI/I’s medical conditions: new approaches to the diagnosis", (2012) it includes as its authors not only history of science researcher Timothy Peters but also neurologists Vijeya Ganesan, Peter Garrard and John Stephenson. Similarly, good costume history not only looks at things like written sources and pictures but also reconstruction work and comparison to modern fashion. The people at Historic Royal Palaces work a lot in the intersection between study and re-enactment in a way that can be very informative. So on, so forth. Wouldn't say it's necessarily as common as it should be, but it is definitely not uncommon to do. There are fields like Big History that emphasise this interdisciplinary study (as well as being super broad, Big History is kind of weird; not a traditional history at all).
It is also important to note that, in many cases, historical forms of an object or practise are not like modern forms. Perhaps some of the things these historians were saying were true or closer to true about historical brewing, and less so in the modern day? I would note, for one example, that historically beer and ale were separate, with ale never having hops, whereas nowadays ale is a category of beer. So things can seem incorrect due to changes in tools, techniques and/or the terminology. Could that sort of things be at play here at all?