I am doing it temporarily on my road bike to use a medium cage RD. Seems to work without problem after a few weeks of riding with it. From what I was able to google, the motion ratio is the same, it just has slightly longer travel that I am not using.
I've never put an 11sp chain in a 10sp rd but the cage would be wider of course and I'd expect some very subtle issues. The 10sp RDs do not all have the same travel range as the 11sp rds so that could get you in trouble depending on the relative positions of the dropout and cassette.