Joel,
we experience the same behaviour and in our environment there's a simple
reason for this:
DIRMC is a quite new option in ADSM and we used it as it became available.
As we already had most of our systems before activation of DIRMC, there are
lots of directories that got backed up before. These directories get rebound
and get new retention periods but data usually isn't moved to another
storage pool doing so.

With all new nodes you should see the directories going to the right storage
pool. I don't know of a simple way to change the pool for existing data.

Best regards,
Michael