It's not a loading screen, the maps are all on the same layer. It's just a clever way of hiding that you're taxi flying to the zone. So potato computers will get there the same time as the rest.
Think of it like flying between zones in TBC through the nether, but with a fancy visual.
Reminds me of how TERA does it's portals. Just a short animation of a mount taking you to a gate followed by an animation of inside the gate until the next area loads.
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