That's not because of the processor. It's because the newest iPad Pro has a 120hz display and the other devices that you were comparing to have a 60hz display.
While 60hz screen refreshes are less smooth than 120hz, the small (but noticeable) of a difference due to refresh rates wouldn't be correctly describable as "stutter".
The M1 processor makes a real difference. I have both the M1 and the most recent non-M1 iPad Pro's.
The M1 processor makes a real difference. I have both the M1 and the most recent non-M1 iPad Pro's.