I'd assume that these processors use the same 'race to sleep' philosophy that Intel CPUs have been using for a while, which would mean that peak power draw would be requested very frequently in short bursts.

The degree of throttling that seems to be occurring does seem to be quite excessive. Excessive enough that I wonder whether they've had unexpected battery degradation in the field, or unexpected degradation of the power delivery circuit, or unexpectedly high load consumption or some kind of fault with the SoC.

Either that or they have just pushed the envelope a little too much knowing that their customers are likely to get fed up and buy new phones... hmmm...