The issue was not the CPU throttling itself, it was the CPU being configured to draw north of 100W and the VRM not being able to handle it, overheating, and leading to the system board hard throttling (down to 800MHz rather than slowly stepping down) the CPU until the VRM cooled down at which point the CPU would be un-throttled and the cycle would restart.
Apparently the power configuration is the one Apple's always used but previous CPUs didn't come close to the current generation in ability to draw power, so they'd never reached the VRM's thermal limits.
By lowering the CPU's maximum TDPup to 50~55W, they avoid the VRM over-heating and while the CPU does not turbo as high as with a 100W TDP allowance it can stay there just fine.
Apparently the power configuration is the one Apple's always used but previous CPUs didn't come close to the current generation in ability to draw power, so they'd never reached the VRM's thermal limits.
By lowering the CPU's maximum TDPup to 50~55W, they avoid the VRM over-heating and while the CPU does not turbo as high as with a 100W TDP allowance it can stay there just fine.