I think it can be rebalanced also but yeah it remains a black hole for most of us until it really happens while having access to this data at the same time.
It would make sense to (by then) assess which cells are poor performers and decide based on the outcomes what to do (i.e. replace cells...
But the good news is that battery cells can be replaced as opposed to changing the whole battery pack.
Replacable poor performing cells is a big plus in my opinion.