I get the impression that they didn't know for sure whether they were going to make a Delta Emerald or not while they were making ORAS.
On the one hand you have this, and the battle resort teasing that the battle frontier was in the process of being built, then on the other hand you fight Wallace in the delta episode and he uses his full champion's team from Emerald, which would be kinda weird if they were planning on doing an emerald remake.
I guess they were like, "idk, just do whatever we'll figure it out later"
