I’ve noticed this countless times even Chashuver people taking 3 steps back at the end of Shemona Esra when the guy behind you is still davening his S.E. This is 100% Ossur.
In all seriousness, how would this work? Would everyone have to wait till the person in the last row finished SE ( especially at a simcha where there wouldn’t be any chairs or tables) and then proceed in an orderly fashion until the people in the front take three steps back?