Right, better be safe than sorry. The important point though IMHO that with Proton and now FEX they have shown that compatibility layers are not that costly or complex :

• try to make it run
• nothing works
• not what doesn’t, try a way
• one thing work and it’s slow as heck
• understand why
• 2 things now work, one of them is fast, the other slow
• rinse&repeat until it’s good enough to crowd source quality control to others

So… I don’t want to diminish how amazing that is, technically speaking, but we now all know it’s feasible. Initially it looks like supporting an entire OS architecture was ridiculous (and it was, emulation was just “good enough” for games that were some years old and for much more powerful machine) until somebody tried “just” swapping or fixing the right API (i.e. DirectX) and … that was actually OK.

Again, it’s a TON of work. A lot of it also comes from Wine. But… now we now why it works and how to do that. Even if Valve were to lock SteamOS, that knowledge wouldn’t be lost on the broader community.