I can confirm that 10+ indexes report. I have one mod that has 12 normally and 14 when loaded after "Gang's All Here". Oh, and Copious containers has exactly 10 I think.
I've noticed if you override a single item multiple times, it increases the indexes; the items do not even need to be modified to increase indexes (the CK likes to leave a few extras in there sometimes, deleting them dropped index usage). The major offenders I've notice modify quest or cells in some way or another. If they made those stop using multiple indexes, it would greatly reduce the amount eaten by some mods. That would literally give a lot of players back 50-60 indexes.
Guess we will see if it helps in due time.