I still unclip my right foot a bit early. I do think it is a signal to a driver behind me that I am getting ready to do SOMETHING a bit in advance, if they are paying attention. Perhaps they don't notice, but that has become my habit. I CAN unclip/stop quickly, I just prefer to do it that way.
I absolutely still do this if I'm riding with others (who may have unusual interpretations of stop signs), am on the road, or if I anticipate needing to stop otherwise. If I'm out on empty roads or the bike trail by myself, well, see my post above.