If that was the case the compute modules would be unaffected. You can't get even those right now either.
The compute modules only has a 5V input, which it must convert to the voltages used by the CPU, RAM, peripherals, etc. using aforementioned power ICs. A modern CPU like the BCM2711 usually has several different voltage domains that must be supplied by the PCB designer, ranging from 1.2v to 3.3v.
There is a fab space shortage. The cost to manufacture goes up and so only the highest volume, highest margin chips get made.