The graph helps but, like you said, it is yet another click away. Before you see the graph you're already conditioned by the "42 FPS average" information. You see the FPS dipping in the graph but you'll think that's an outlier. The average is 42 FPS after all, that's nice amirite.
Personally, I feel like the solution is that the Steam Verified badge should mean something. Solid 30 FPS should be the golden standard. If the game is frequently at 15-20 FPS then it should be "Playable", not "Verified". The current criteria where typing your name with a virtual keyboard means "Playable" but running at 15 FPS is "Verified" is not helpful.
These charts are good for those games that are incorrectly marked as borked or don't have a verified status. You can now see evidence that people are playing the game, and that's nice.