Indeed. Moulins in the Tour last year is the only example I know of where the rule was in effect, but the gap still large enough to count.Actually amazed by how many GC riders still try to finish somewhat up front in stages like this. Since the 3s gap rule the chances there is actually a gap being counted are incredibly small, it's way better to just cruise in the 2nd part of the peloton the last 3km than around top 20-top30 where crashes often occur.
Completely different in technical finals where gaps may actually occur ofcourse.