your point is valid, but it feels wrong not to accept it for Macbeth. It's known as being Scottish. entering the UK for Macbeth, although correct, just doesn't feel right.
It's better than putting 'UK' as 'A Clockwork Orange' already accepts that. I admit it could be accepted but then you cannot use MacBeth either. Plus, Scotland was a country in the time it was based, both in the play and the real life character it is based upon.