"Well, we might not want to say "any patch on trunk can be backported to any branch, no problem" because that can often have undesirable side effects."
Granted, the question is how can what is allowed be more obvious and more explicit so its less likely someone will be waiting for approval mistakenly?
As for the unnecessary delay before it was made clear that this was a wide impactor. I'm sure an invitation for people to nag in upstream tickets more won't go...unrewarded. Something for the day-to-day Fedora Mozilla package maintainers and triagers and possible FESCO to be aware of.