On one hand you’re absolutely right. Cheating can and should be dealt with using server side validation tools without needing to use invasive rootkits with spyware-like and keylogger components on our systems.
On the other hand, I’ve been very impressed in Valve spearheading the movement via Proton and the Steam Deck to make Linux users impossible to ignore. There are many approaches that could have had an “Only Steam-Deck compatible” solution, but Valve didn’t go that direction. Now Linux gamers everywhere benefit, and developers don’t lose out from what’s now a significant gaming userbase, many of whom are also technically inclined and willing to bring feedback to the developer.