Yes, I believe unit wide and ranch only are grouped together in private. As far as "intentional," yes to some degree, since that is the way their bookkeeping works (public tags separate from private tags).
No matter how they broke out the success rates, it wouldn't be an exact picture. Public tags are valid on private land, and some unit wide private tags get used ranch only, so there is no way of knowing the exact success percentages on public vs private land without adding a bunch of effort, and to do that would probably raise tag prices to accommodate the additional management costs. I'm fine with it the way it is. It's good enough for the G&F to manage the herd, and that's really the purpose of the success rates, not to make hunters choose the right area to hunt (success rate doesn't mean a darn thing if you don't know how to hunt).
Let's also not forget, the success rates even as they are represent a guess to some degree, not everyone returns their harvest results, so the G&F projects kills based upon the returned results (run the numbers, it's not just number of reported harvests divided by # of tags).
Additionally, the harvest data is only as good as the people who are giving it to them (i.e. hunters, and I have no doubt that some of them lie on their harvest reports, further skewing the data).