That’s true for sure, but that doesn’t mean that it’s valve didn’t do an absolute fuckload of work to get proton to be actually functional.
Getting direct3d and vulkan working with actually useful performance was the turning point for Wine being useful for games in addition to just standard applications.
They definitely spent an ass-load of money on that and the fact that Wine was around for 25 years before that just goes to show that no one else was willing to do that.