they said they had a similar stance to not letting BLU equip KC/Joyeuse/Ridill, and now BLU can use OAT and OA2-4 swords.
Two different dynamics.

Dealing Damage with multi-attack weapons is offset by the fact that the damage values of these weapons are low and the fact that both you and the monster are gaining TP at an enhanced rate.

Curing, however, does not come with that balance factor, Cure V in particular being even more-so with this as it does not come with the potentially dangerous hate spike Cure IV can provide. Furthermore, the additional traits and abilities White Mage get to make it a superior healer is not always necessary for a number of situations. Giving Red Mage and Scholar Cure V puts them in direct competition for a slot that the developers pretty much perceive as designated for the White Mage to fill, as curing and status removal is the root selling point of the job, offering little else.

Keeping the healing performance so widely differentiated helps White Mages keep the position they have, one that the developers had to piratically redesign the job to wrest from the hands of Pink Mages.