The difference is that the way they do it they don’t need to have the MCU running. That is they can receive a SMS by having only just barely enough compute power active (then if it is an appropriate Wake Up one then it un-sleeps the MCU which then brings up the rest of the car).
If the MCU is running - to actually maintain a data connection or do any other interaction with the mothership to wait to be woken up then the car isn’t “asleep” (ie it will be just like when sentry mode is on as far as hourly power draw).