Comment by bayindirh

Your cell phone modem is completely decoupled from the main processor and is a complete, independent system in itself, so it's optimized to do that.

Bluetooth and WiFi radios on Macs are also semi-independent. They can keep connections alive while the system is in deep sleep.

Waking a big processor, frequency scaling it and turning it off is surprisingly complicated. We disabled SpeedStep in our clusters since frequency scaling visibly affected performance of the systems due to overhead incurred by frequency change. Same is true for waking / sleeping big silicon.

It's complicated, it's wasteful.

Some of the Intel's biggest improvements as their micro-architecture evolved were reduction of the frequency scaling overhead and its performance impact, but this never made the news back in the day because its effect was invisible in consumer class systems even in its most primitive form.

> Maybe it decided to do some other stuff while it was awake?

That's called Power Nap and is enabled only if your computer is connected to power, by default.