I think that’s a question for the RHS! Another example of the botanists retrofitting species and their hybrids, I think. I have seen more recently some nurseries in Europe selling this cross as Stone Praetorian, but most seem to prefer YT for both the stonei and platy crosses. For what it’s worth, Koopowitz advises in his Tropical Slipper Orchids book, trying to get a true YT (using platy) as he obviously considers it superior. I doubt there is little difference in the outcome of both crosses, although I have observed YTs seem to be larger & paler, SP with redder pouches.
My SPraetorian is quite red.