But when LHR hear the call "United 123". he has a flight plan, LHR have the detail and there is a squawk on Radar. Not too difficult to confuse.
I am quite happy that if I rock up at Goodwood and say "Goodwood; good morning BUIK" and they say "IK pass your message" and I say "green PA-28 IK inbound to land" that makes everybody's life just that smidgin easier.