That's technically true, of course. However, that sort of shorthand is used very often. It is an aspect worth noting given the amount of newspaper commentary telling us that the "metropolitan elite" voted to remain, or that only young people voted to remain
etc. There may very well have been analyses attempting to show that people with different hairstyles voted differently for all I know, or people who open their boiled eggs from the top or the bottom.
Certainly it makes sod-all difference to May and her wonderful deals, but if one of the countries of the UK has an electorate who voted 62% to remain, that is something worth noticing. It might not be important to many, but it adds to the whole "getting Tory governments when not voting Tory" aspect of things, and might have implications for the future.
As a tangential aside, is anyone else annoyed by the "everyone over 35 or so is an ancient useless evil bastard and voted to leave and is therefore guilty of ruining the future of all younger people" narrative? And the "everyone who voted 'leave' is a terrible dim-witted racist bastard" one? That level of discourse is pretty poisonous.