I just tried this myself on my PRIME Z370-A (different ME version update is available) by using the GUI. After it updated, i tried to run it again even, thinking it would wisely tell me its already updated, but it just re-updated again.
Anyway, checked the version in UEFI welcome screen and was indeed updated.
I will revive a computer, z390 and will test these with out before jumping on it. and how afect on normal and gaming operation. will be thr 4 build in the week. but basic is a add fix for another cure for spectre on a motherboard cpu level
Also that it has to be mix with a MEI driver that IS Not on the asus website. i will try all scenarios in the faster mount the time. since most analysis take time. I will post back on a post Saturday.