Every time I buy a Windows-only game in the hopes that wine or a 3rd party native binary will make it work on my machine, I am counted as a Windows user, even if the game ends up not working for me. This make any statistics gathering mechanism less than worthless. In fact, it self-reinforces the idea that a Windows version is always sufficient. At least on Steam, with the automatic proton/wine service, there might be hope that stats are more accurate, but even there, it's up to them how to account for users. There really isn't a fair way to do it, other than intrusive network statistics, which I always disable and which probably don't distinguish between wine and real Windows, either.