I suspect the metrics are actually better than reported.
For example, Skul: The Hero Slayer[1][2] is a relatively popular indie game whose Steam Deck compatibility is officially "Unsupported" because "graphics settings cannot be configured to run well", but if you ignored the warning and installed it anyways, you'd be scratching your head in confusion trying to find anything broken compared to PC. Imagining NEOWIZ/SouthPAW Games is liable to have lost quite a bit of revenue because of this seemingly incorrect compatibility listing alone.
[1] https://store.steampowered.com/app/1147560/Skul_The_Hero_Sla...