Well, also don't forget that even back in 1.0, it was made pretty clear that the Primals are definitely aware of each other's existence, but, they definitely are not allied with each other, and seem to regard each other as lessors and themselves as the 'one true god'.

Ifrit especially had this attitude - in 1.0 when he first tried to temper the player unsuccessfully and realized they were protected by the Echo, he actually thought that the player was already tempered by another Primal (stating that he detected the "taint upon their soul"), and specifically mentioned Titan, Garuda and Leviathan while at the same time belittling them and making the player swear that they "shall forsake the summoning of another" (Primal).

Although ARR retcons a lot, I'm liable to regard this as still officially canon (especially when viewed with Ferne's statement Moose posted above).