I’m pretty sure it is a wrapper in the way it looks up game-specific information to apply specific tweaks to how the game is ran and how the prefix is set up… But it is also true that it does also include a modified version of wine, so the terminology is difficult to pin down.

That said, I don’t mean it in a disingenuous way, at least I don’t think it is such. I do believe valve is often attributed excessive credit for proton’s creation, but I don’t think they did anything wrong, much less “just nab it”. Open-source is open-source, and I’d imagine people who put work towards making wine viable are happy that Valve brought it to the mainstream.