I've been alternating between the same two MTBs for the last few years - they're super similar in geometry at sag despite one being a hardtail and the other an e-FS. I always ride flats, have never used clip(less)s. Anyway, I recently noticed that I tend to place my feet further forwards on the hardtail, pedal axle pretty much right in the middle of each foot, whilst on the FS my feet are further back with the axles a bit behind the balls of me feet.
The bikes are almost exactly the same wheelbase, but the hardtail has about 20mm more reach / front-centre and 20mm less chainstay length. And I'm putting my feet about 20mm further forwards on the hardtail vs the BB, so I'm in the same place vs the wheels. Coincidence?!
I think your midfiot position is instinctively to stop your feet getting bounced off. Less of an issue on the full suss, but midfiot would help there as well
I did wonder that but I also wondered if I'm naturally moving my feet back under me to compensate for the slacker seat angle and shorter reach of the (less ideal) geometry of ye olde Levo? (This is the sort of thing you start thinking about as you're stuck in admin deadline hell at your own business when you wanted to go and play bass at a jam night instead...)
It's both things IME (geo compensation & hardtailness)