As I read it appears that apple not on has you keep that key to unlock such things but since it's on time machine, rather than guess why not make the call to apple. This work appears to be worth it.

My bet is a call to apple is cheaper than

I always want to ask but at the risk of upsetting folk, why do folk encrypt without a backup in the clear that one can just copy their stuff back in?

Even I have 2 copies on HDDs, and a few select items synced with a cloud and a final can't lose this ever on all the prior backups noted on a few memory sticks.