Other distros have been competing forever. SteamOS is built on top of Arch, which updates multiple times per day. Valve pushes a lot of updates tied to the Steam experience, some of them are also shared with normal Linux desktops, so that makes it somewhat of a moot argument. I run normal Linux (Fedora Workstation) and play games with Steam, and they run the same as my Deck, even day 1 releases.

Like, I get the appeal of a Valve-blessed Linux flavor, but as far as their stack goes, the Linux side of SteamOS is somewhat conservative (not many updates) and limited (due to read-only OS images) compared to normal Linux distros and the gaming side also gets pushed to all Linux distros. As a Steam Deck owner, I personally think Bazzite is more interesting for a real world gaming desktop usage than SteamOS, where you can't even print documents because it lacks the required stack!

To show how conservative it is, I call recall a few examples:

The desktop side, which runs the KDE Plasma desktop, was stuck on version 5.27 for ages and just got recently updated to 6.2. Meanwhile, Arch and Fedora/Bazzite are rocking Plasma 6.3 and should receive Plasma 6.4 in a month or so, pretty much day one.
The Linux kernel (although patched and tweaked) in SteamOS was still on 6.5 until a few days ago. It was bumped to 6.11 with SteamOS 3.7. Meanwhile, Arch and Fedora have been on 6.14 for weeks now, with new hardware support, performance fixes for existing hardware and some new features.