With all due respect, @WhatNextCatsAsDoctors, an awful lot of people have either deliberately or innocently been misinterpreting the Equality Act for the last 15 years.
The Supreme Court judgment supersedes any contradictory interpretation which might have been adopted prior to now, which is why many "big orgs" like the one your infallible friend works for will now need to go back to the drawing board and rewrite their policies in accordance with the actual law.
It is astonishingly arrogant to come on here and say that you're the only person who understands the law, despite the fact that (a) everyone else here disagrees with you, (b) some of us, unlike you, are actually lawyers, and (c) the best lawyers in the field agree with us on this point and not you.