I think it's a good thing to do anyways. It shows that there's a solid market interest in gaming on Linux.
Whichever platform you play a new game on the most during the initial two weeks after getting it will be registered as the platform you bought it for.
E.g. play a Windows-only game for two weeks using Proton and both Steam and the gamedev will see it as a Linux purchase in their stats. Meaning they get actual numbers how big their Linux demographic is.
Does that remove the Windows purchase too? That could be seen as 2 purchases for the same game.