Yeah as an Arch user I disagree. Imo a handheld meant to be a plug and play system would hugely benefit from a stable OS with a laid back update schedule. You don’t see PlayStation pushing constant updates the second BSD packages get new versions.
As others have said, Valve has their own immutable release system, so it doesn’t really matter. In this case, the rolling release has even less to do with it. They likely chose Arch due to the up to date packages which benefit gaming.