I see 1 on1 bees in front of my hives, all the time. On bee stands there and the other one grooms it checking it over. Occasionally I see 2 or 3 on 1.
Did the bee under attack land there or did it come out of the hive.
Hygienic bees will not only clean each other, they will also remove a bee that is sick. My bees use my pool as their trash dump. I have watched them carry bees off the front of the hive and dump them in the pool. The bees they dump had DWV.