In CA there's also the issue of not having electricity in the first place sometimes though. So power _consumption_ seems kind of secondary.
These chips don't run at a fixed frequency. They dynamically adjust based on thermal limits and power limits.
You only have to burden most of the cores/ALUs to hit maximum power. Any load above that threshold uses the same amount of power, as frequencies nudge down to compensate.
The power limit is configured in the BIOS, and can be disabled, but with these massive chips they default to throttling down and capping power consumption so that you aren't forced to go crazy with the cooling system (and motherboard and PSU capacity).