AFAIK low-power MCUs are always used in race-to-idle fashion because nothing beats <<1 µA sleep. For computer processors, DVFS isn't used like OP suggests, it'

AFAIK low-power MCUs are always used in race-to-idle fashion because nothing beats <<1 µA sleep. For computer processors, DVFS isn't used like OP suggests, it's really more like Dynamic Temperature And Power Scaling (DTAPS), because it's meant to extract maximum performance from available power and thermal budget. Also while CPUs _do_ change power and frequency at >1 kHz, they're intentionally designed _not to_ downclock in the example GP gave (inter-frame idle).