In part, yes, but the whole picture is a bit more complex. Intel and AMD both work with vendors to work out reference designs and power regulator configurations that are compatible with their CPUs. Modern power regulators are relatively complex, especially when you get into the high-end desktop and server space. There are a lot of things that can be done wrong and cause issues, such as voltage or current overshoot when the CPU moves between different power states (e.g. low to high load).

That I/O die will do little if sent hundreds of amps all of a sudden.