Thanks Bobby, the 8 day info helped a lot.
After further investigation it gets more strange. On the EHD transfer screen when sorted by Folders it doesn't list any (older than 8 days) prime time shows at all but when I switch the sort to No Folders it lists a few but not all. When changing the other sort from DVR Date to A-Z different shows appear for on the list. All the lists no matter the sort criteria are incomplete, even omitting non prime time shows. In fact on all the lists there is a vertical scroll bar that seems to indicate more content that won't display when scrolling up and down.
I've never seemd to have a problem transferring the things I've wanted to transfer, which have been mostly movies, but I can see where it could be a big deal if you have to move your unwatched shows off the HWS if you have a problem and need to replace the unit.