it clearly runs at 30fps. using frame advance on the player shows only every 2 frames of video footage gives a new frame on the Switch 2 screen.
at first I thought each video frame is also a new game frame, but it's actually just the slow pixel response time of the Switch 2 blending the 2 frames together (or it's intentional motion blur... but it looks more like slow pixel response)
checking this takes like... 10 seconds, so why on earth, if he's not sure, didn't he just look at his footage for 10 seconds, go frame by frame, and see?
edit: here I took 10 consecutive frames from the video, and labeled them like I think it corresponds to the in-game frames.
(btw. how insane is webp? this 1080p animated webp image using 10 frames is less than 2MB)
the surroundings (fingers, system itself) cleary move each frame, meaning it is indeed a 60fps video feed. but as you can see, the in-game frames only really update every 2nd frame. meaning it is locked to 30fps.
here are all frames separately in full quality: