This is a fascinating subject. The only pianist I've ever noticed using a lot of fluttering is Martha Argerich. I saw her two nights in a row, and the second night I could see her feet very clearly. Both nights she was playing Prokofiev 3 but in different halls.
I assume most pianists instinctively keep the pedal somewhere between on and off, and half pedalling and flutter pedalling aren't so obvious to the onlooker. The difference in pedal travel between fully damping and fully clearing the strings usually isn't very much.
Of course some pianists allow the pedal to come all the way up and can look like they're slamming the breaks on when lifting the dampers, and it's certainly safer when playing a piano other than their own. I attend a fairly major piano competition every few years (in the audience 😃) and these things become more apparent when several pianists play one after another.
It's interesting to compare pianos and how pedalling can affect them differently. Old Bechsteins, for example, have light dampers, and replacing them with heavier dampers can make the piano sound too dry. Steinways have heavier dampers, but the duplex scaling gives the sound a lively shimmer, which doesn't immediately disappear when the strings are damped.
