This is also all over the internet and we even have
AllHairMatters being banded about.
It's guidance.
No one has said you can't do colour and cut. No one has said you can't do black hair because it takes longer. (Article I read)
It's just people like to have a tantrum over things they don't even really seem to understand.
Guidance is not law.
This is a public health crisis and within the law they must publish guidance about how to possibly reduce the risks. Less time in a room is just one.
There's nowhere that says by law you must only spend 20 minutes per customer and you must only cut their hair.