This pdf (https://f.hubspotusercontent30.net/hubfs/8968533/CS-2%20Data...) says the power supplies are 6+6 redundant 4kW supplies. Assuming 100% utilization (not realistic, but it makes the "math" easy) that's 24kW of "power supply".

If we presume the wafer consumes a large percentage of that (say 20kW out of the 24kW max) and that they are feeding the "wafer" with DC at 1v, then they /do/ need to feed in 20,000 amps to deliver 20kW of power at 1v.

So yes, 20kamp is a lot of current, but it is within the "power budget" the device seems to express in its marketing material.

Core voltage is going to be in the ballpark of 1V, and given the stated power consumption is 15kw that means a minimum of 15kA. So, it is indeed a lot but the math checks out.

7nm core voltage is 0.75V. If they want good reliability, 0.7V underdrive is understandable. So, 2.2kA at 0.7V sounds reasonable to me.

how much of that power actually reaches the chip though? (it's hilarious that this is one chip)? this thing is mostly a water pump - I just can't - everything about it is just wild

Most of it. The water pump and other stuff consumes probably less than 500W total. There's some efficiency loss in the actual power converters, but they're likely designed to be >95% efficient (probably >98%), otherwise cooling them would be a nightmare.