At best, it's pretentious academic behavior.

Tbh I think it's people just reading theory and using similar language when they discuss things having been influenced by that theory (or by people who have read it because let's be honest on the internet not everyone reads theory).

I had a post here years ago petitioning to use burgher on the somewhat serious grounds that insisting on using the one that can't be deduced from usual English rules in English is antiworker.

This is an awful idea. Idk if most people even know what a burgher is, and if they do they probably don't associate it with capitalists. It's possibly even worse than bourgeoisie because I think more people have heard of that, or at least know what bougie means. Those aren't the only two options though, one I've seen before and seems the most straightforward is to just say 'capitalist class'.