> Process：Manufacturing with 28nm process

standard Vcc for 28nm is 850-1050mV (varies based on the exact process)

so yeah more like 100A and probably that's all going through the pins without on die power regulation

The inductors are still too big to be on-chip

Intel only recently introduced this feature, and it surely required a lot of R&D. At the time they were most likely the only one, and may still be.

IIRC, the only part they replaced was the controller IC itself. All of the main power components (switching transistors, filter inductors and capacitors) remained off-chip.

Consider that the VRM's have as much or more silicon in them than in the host processor, and they have completely different breakdown voltage and switching speed requirements relative to a CPU.