this is the reason why Asus release theIt could absolutely use twice as many dimming zones, in my opinion. But you have to remember this is also still only a 27'' panel.
I don't have any pictures, but i'm pretty sure you can look at some reviews that will show you it. You don't really see the haloing if it isn't a scenario like you describe, whites on top / next to complete black.
PG27UQX with 576 zones.
In any case those monitors are not ready to be marketed, too few zones and fans, really? fans in a monitor?
New Asus PA32UCX have 1150 zones, that is a FALD monitor, not those ones