The whole discussion is futile anyway--especially on enthusiast boards like this one. Apple has to consider the entire iPad user base when making any iPad hardware or software, whether it says "Pro" after the title or not. In Apple nomenclature, "Pro" just means "nicer", or perhaps "nicest". Sure, there are four different types of iPads, and you could easily fork one of those lines off into its own thing and stick macOS on it. I doubt it would be an issue from a technical standpoint, and I'm sure Apple has messed around with it internally.
There is no reason for Apple to create this as a real-world product.
The kind of iPad users that want a full blown desktop productivity OS on the iPad Pro, even if it's not macOS but just a more fully featured iPadOS that just works more like macOS and less like iOS, are not the kind of users that Apple is marketing to with the iPad. They never were. They're marketing the iPad to people who want a simpler, more focused, and more portable way to do some very specialized things with the same fluidity as they can on an iPhone, which is the vast majority of iPad users. And the marketing for the Mac is easy: they just need to appeal to people who prefer to work on a traditional computer and prefer a laptop form factor, which is the vast majority of Mac users.
We have watched the iPad Pro go from "big iOS" to iPadOS 15 in the last 6 years. We have watched it get more and more and more powerful chips (then flat out Mac chips!), more and more RAM, nicer screens, and awesome new designs. But the very essence of an iPad is a more approachable computer. The demographic it appeals to the most does not want macOS. In fact, most of the features in iPadOS that make it iPadOS are things that most iPad users either don't care about or will never find. Most of them also couldn't tell you what their iPad's software is even called or that there was a keynote a few days ago about that very topic.
The main purpose of the iPad has always been to be an iPad. If giving it the same hardware guts as a Mac and then not putting macOS on it isn't proof enough for some people, then I don't think anyone is going to be convinced at this point. And I think if it were planned for next year or the year after, there would be more smoke to signify a fire by now. There doesn't seem to be anything like that in the works, and Apple has flat out said multiple times that they aren't doing it. I don't think they really care what the Macrumors forum posters think about it--that's a very tiny storm in a very tiny teacup.