SteamOS is also an Arch distribution, though I'm not sure how significant the changes are. AFAIK Lutris uses Ubuntu's libraries for better compatibility across distributions, maybe Steam does something similar.
kinda, SteamOS is an arch distribution but it's locked down by default (you can access stuff) and it's run by the company selling games on PC, so they make it work.
On a normal arch distribution, you have to deal with installing dependencies yourself, so more of a pain.