Once you're used to flats, this isn't an issue. If you have good pedals and good shoes, your feet don't normally move at all.
Re:Myths in cycling: wider tires are slower
by matthewowen on Monday June 14, 2021 @07:33PM
(#27509718)
I mean, I ride flats on my mtb because the trade off makes sense, but I absolutely wouldn’t do a hard sprint out of the saddle in them like I would on clipless on my road bike.
This is relative to casual toe clips or flats. Compared to old school clips + tightly fastened straps with dedicated shoes they aren’t a huge difference performance wise but no one rides those any more because they’re much more dangerous and much less convenient.