Interesting topic, must stress them terribly but it's legal so there it is.
I would imagine that the animal is stressed for about three minutes after it's caught then it realises that escape is not possible and 'something' is holding its paw. After which they curl up and wait/sleep. Then they probably get agitated upon the trappers approach. In the grand scheme of things that's not much stress IMO.
ive seen a fox rip its paw from the jaws of a terrier. there must be a fair amount of pressure in those jaws. and i would think they will be trapped for a fair timespan. of course the fox is stressed. ffs. its interesting to see how things are done all over the globe and i wouldnt knock other cultures. but lets not go down the road of sugar coating things. interesting post thanks for sharing. but not my cuppa tea