It just shows that Valve themselves don't take that survey seriously, if they don't even count specialized hardware targeted for SteamOS. So I wouldn't use those numbers for any far reaching conclusions.
I tried using Linux on several occassions over the last 10-15 years. It was never easy or fun. All the GUIs felt like they were from the 90s and nothing worked out of the box. I tried Ubunutu, Mint, Arch, and a few others. My last attempt at it was ~2014. Maybe I'll hate myself enough to try Linux again in a year or two...