Hithere
It is about the implied significance you are to a word
What if they had said " there's someone at the till, an young / middle aged / blonde/ etc woman/man'" - would that offend anybody
I guess it depends on whether the young/middle aged/blonde etc woman/man was sensitive about the aspect of themselves that the speaker took it upon themselves to choose as an identifier, and good manners dictate that that is not for them (the speaker) to do.
If it were a Question Time audience scenario, and an individual needed to be pointed out in a crowd, it would always be something impersonal that was chosen to do so - 'The woman in the red top' or 'the man in the blue tie'. Fiona Bruce would never say 'the bald man with a big nose', or 'the old dear with the blue rinse', would she?