No part of a person's body ever goes backward relative to the ground while they are running. The wrist is always moving forward relative to the ground, or at worst, is stationary. So your wrist is not traveling further, it's just not traveling at a constant speed like your belly button.
I've also done tests where I have run with a GPS on my wrist, carefully following a course I measured with my bike. I didn't see much difference in accuracy when compared to a bike mounted GPS or a GPS I was wearing on my wrist while biking.