I haven't personally, but Trev has when I've been with him.
We were walking our dog one day and a group of 6 jws were on the corner, just getting ready to start their fs. I knew them all, and Trev knew 5 of them, and as we approached them on the same side of the road, they turned their backs on us almost in unison. Trev commented, loudly enough for them to hear, and for a couple we know who were walking towards us to hear as well, that the jws had invented a new sport, "synchronised shunning", and wondering if it might become an Olympic event in years to come.
The couple, who know from talking to us how jws treat leavers, laughed out loud. The jws didn't seem to be amused.