As an aside, Pluto T5 does currently work when being used in a Non-Steam Steam Proton prefix. I can only assume this is another side effect of Bottles not quite yet working with Proton well (it has more than a few issues that breaks things, like, a lot atm).
Pluto T6 (Black Ops 2) works fine in the same Bottles prefix, so iunno. :shrug:
honestly, just another reason why Wine-GE shouldn't have died tbh.