"SO you are saying this hub die has this defect in it that caused the appearance of doubling to the right side?"
No. If you were to print an envelope with a hob die, the indicium would be the mirror image of a U311.
I am merely speculating on there having been a hob component that was used to "freshen" the working die (or possibly freshen a (complete design) hob die, which then was used to freshen working dies).
Examine this Die 88b, Cap on 2:
Notice the doubling on the outer tooth line, left side. First, observe that all teeth are doubled in exactly the same manner. Would you expect that if the scenario was an engraver was freshening the die tooth by tooth? Secondly, observe there is no doubling on the rest of the tooth lines. How does this happen?
Fun speculation. This is why I love to collect envelopes.