Before when sorting by author, all titles under that author would be in alpha order. That's the sort that's off. At least I could swear that it used to sort that way.
If I'm indeed imagining it (it sounds like I am at this point though
), yes, I'd say it would be a great feature to add into PRS+. Maybe I'm thinking of finding books easier through the folders option.
Edit: I also checked the sort if it was by date possibly, but that's not the case either. It really just seems to be somewhat haphazard, and different on different ereaders with the same identical books loaded on them.