ICC Update Broke Adaptive Mounts
To be clear, yes, this is intentionally changed behavior, and we understand it is not ideal.
In this patch, because of unique and significant complications with how Dalaran works, we had to make a decision to allow all or none in Dalaran.
We intend to sort this out entirely in a future patch.
We looked into it, and this is not a bug.
This a deliberate result of how the no-fly zone in most of Dalaran works to prevent some mounts from being able to fly in from outside of Dalaran, land, and take off again. It’s only having this effect on flying mounts, so players can still move around Dalaran at ground riding speed (wherever riding is permitted in the city).
And all flying mounts may be used within the Krasus’ Landing part of Dalaran, as intended.