I think he knows they are the same thingNo difference at all, it is merely a name some collections use to make their tigers sound special - all the moreso when you consider outside of India there are no Bengal Tigers at all, and thus these animals are invariably zoomix individuals.
Interestingly though, the name "Royal Bengal tiger" isn't a zoo invention, it is because during the British rule in India leopards were called tigers. So the Royal tiger was the actual tiger. The name is just a hold-over from a past era.