Yeah, even though Asus has managed a lot lower VRM temps (on OC3D's testbed)------ really, none of those temps is bad or even just ok. They are all very good. The MSI Unify is edging into "ok" territory. But still, the temp posted there, is fine.https://www.overclock3d.net/reviews/cpu_mainboard/gigabyte_z690_aorus_master_review/21
You can see the VRM temps comparison here
I would guess Asus used a magic mix of 1. large heatsinks 2. maybe used really good thermal pads 3. the specific components which they use for their VRM, may naturally be a bit cooler. I haven't yet seen any good comparisons of the VRM components for Z690 boards. But Asus often doesn't use the same stuff as the other brands. (and in the past, not necessarily better).
I still have a hunch that Gigabyte heatsink may fair relatively well, when actually used in a real computer case situation.