It was like this on the dev and carried over to the live. There is no reason to use it over the fox if you have the fox given they are the same BR and the fox is notably superior.
The GR4 with 20km IR PGMs is the only real addition for the UK tree this patch.
I think its due to having a stabiliser and not beam riding, though few things follow that rule, like the Stormer is Stabilised and should be able to fire when moving but cant due to Gaijin
We do not have a 100% undeniable proof. We have a Brochure of the missile itself that states it can be fired on the move, right next to ZT3A2 picture, but Gaijin says their Consultant states it can’t.