Question regarding all enhancement when enabling xmp. (ASUS z270e & i7 7700k)

[Boergeiam]

I just have a small question.
I'm messing around with my system, and for some reason i noticed that i hadn't enabled XMP on my RAM (rookie mistake. I know). But when i do enable it, i get the option to also enable this "all core enhancment [ACE]".
When i have it on (XMP and ACE), my CPU is always maxed out at 4,5 ghz, never clocking down.
When i run the PC with XMP on and ACE off, my CPU won't boost above 4,4ghz in games or anything, where as it before perfectly fine hit 4,5ghz.

Any idea why this is? My guess is it is some motherboard thing that turns on, but i can't see an option anywhere that would say it can't boost above the 4.4ghz, even the bios says the max turbo is 4,5ghz. Upon exiting the bios it shows a list of changes, and nowhere in there does it say anything about some 44x multiplier for the CPU.