As I understand it, the complaint isn't about battery life during usage. The issue compared to a mac is that I could close the lid on the macbook air m1 that I'm typing this on mid sentence, and then open the lid in two weeks, and have lost basically 0% battery.
I'm not sure if that's possible on windows. I know my work laptop doesn't work that way, but then, it probably runs all sorts of enterprise settings.
I'm on an AMD machine that System76 wrote the firmware for, and they specifically wrote in S3 sleep functionality despite the base firmware missing it.
The firmware vendor contracted System76 to develop the feature specifically for Linux compatibility.
I'm unaware of how much access Framework has to the underlying firmware blobs. If they don't have source/license/keys/etc for the right parts, they might be at the mercy of their own vendors for S3 support.