Don't know if there's an official name for it, but you're just flashing between clip a and clip b as a transition. There are more than one in this section if you look. I have created it myself, but don't know that I've posted it anywhere. I may have to do that.
You could do this manually very easily. Clip A or Clip B needs to be superimposed above the other. The one on top, you just use the blade tool (command-
to cut a frame or two out ever so often.