Well they don't have to put the great apes into one baramin. And since it would raise awkward questions, they probably wouldn't.
I saw a website, I'll look it up if you like, where the usual rule the guy used was that a baramin was usually what a taxonomist would identify as a family.
Except when it came to the apes; in that case genera (for example
Australopithecus) got their own baramins. They need to split as much as possible when they get near to humans, and lump as much as possible everywhere else.
This, of course, makes it difficult for them to come up with a consistent method. That and the whole "being wrong" thing.