It the names are not registered they might only be 'trade names' rather than 'official' names and it might not be possible to trace back the parentage to the species involved.
I've come across cases where a trade name can actually cover a range of very similar plants all sold under the same name, but all slightly different. I've seen lots of cases of names which you can google and find places selling under that trade name (or pictures of ones people have bought under that trade name) but they are not registered.
It's strange because usually I've not seen that with a cross named with two parents trade names, that makes it look more like a registered name
As I understand it the RHS is where they would be registered for both the USA and European hybrids.