Yeah the LDOs are like FIVR was on Haswell. But so little is known and written about it it's hard to find, you really gotta dig it out, so they went with calling it Vcore in UEFI since they are related but IMHO there is additional stabilization on the CPU itself which reduces the voltage a little so little that it couldn't be done with FIVR. Yes on Haswell you would set Vccin for the FIVR and then Vcore which the FIVR would convert to. Now you can only set the "Vcore" you feed to the CPU where LDOs drop it and stabilize it automatically to a lower true Vcore.
There are articles and podcasts about it. Another is the presence of many capacitors on the underside and the fact that 22nm wouldn't handle so high Vcores with so good power consumption people feed now to 14nm so there is an obvious hidden V drop. My guess is the drop is about 0.2V. Which was the lowest limit FIVR could do before, I use 0.3V on my FIVR to not run into issues. Intel doesn't really talk about the LDOs much since it's too technical for their marketing department