Valve’s Pierre-Loup Griffais addressed the topic on Twitter, first acknowledging his comments regarding the Steam Deck targeting 30 FPS. What that means is that 30 FPS is the minimum floor that Valve considers “playable.” It’s not a cap or a limit of any kind. The Steam Deck is “targeting” that every game played on it exceeds 30 FPS.
Source: N4G PC Steam Deck 30 FPS Concerns Addressed by Valve