As a clean shaven person I have no skin in the game. The cynical side of me thinks "what do they know that we don't? Pandemic 2.0? Widespread use of CS gas for the expected unrest?" But I've run out of tin foil, so...
You'd think that if they can make exemptions for cultural reasons then everyone should be offered the choice, otherwise perhaps they're leaving themselves open to claims of discrimination against people whose culture isn't deemed worthy of exemption.
There will be exemptions for religious, cultural, disability or medical reasons. In these circumstances, the force is seeking to introduce an alternative type of respiratory protection.