The devs from ΔV: Rings of Saturn give a completely different story. Yeah, most bug reports come from Linux - but platform specific ones a vanishingly rare: https://www.reddit.com/r/gamedev/comments/qeqn3b/despite_having_just_58_sales_over_38_of_bug/
Do you know how many of these 400 bug reports were actually platform-specific? 3. Literally only 3 things were problems that came out just on Linux. The rest of them were affecting everyone - the thing is, the Linux community is exceptionally well trained in reporting bugs. That is just the open-source way. This 5.8% of players found 38% of all the bugs that affected everyone. Just like having your own 700-person strong QA team. That was not 38% extra work for me, that was just free QA!
Not to mention the quality of the reports from the Linux users was vastly more details and useful to them.
I bet most companies will just take that extra 30% as profit rather than giving it back to their users like proton has.