I'm pretty sure this is due to how the set was dispersed, but could be wrong.
You could purchase
packs of singles and the panels came in some sort of
"Hanger Set". The Feller on the right would have been the top part of a panel (see the small tabs on the bottom of the card) and the one on the left would have been pack-pulled.
I think this is the case for all of the cards in the Red Back set. (uncertain of Blue Backs, haven't put that one together)