It'll almost certainly have something like this or there's no point in them making it at all.

GoG has native games for Linux, at the time the feature was initially requested to GoG Proton wasn't a thing and we had to do janky stuff to run windows games on Steam. I'm not saying GoG won't do it, I'm saying people are assuming it will just because everyone else does, which might not be true. Hopefully it is, but it's just an assumption.