I have an M3 for my personal laptop and an M2 for my work laptop. I get ~8 hours if I'm lucky on my work laptop, but I have attributed most of that battery loss to all the "protection" software they put on my work laptop that is always showing up under the "Apps Using Significant Power" category in the battery dropdown.

I can have my laptop with nothing on screen, and the battery still points to TrendMicro and others as the cause of heavy battery drain while my laptop seemingly idles.

I recently upgraded my personal laptop to the M3 MacBook pro and the difference is astonishing. I almost never use it plugged in because I genuinely get close to that 20 hour reported battery life. Last weekend I played a AAA Video Game through Xbox Cloud Gaming (awesome for mac gamers btw) and with essentially max graphics (rendered elsewhere and streamed to me of course), I got sucked into a game for like 5 hours and lost only 8% of my battery during that time, while playing a top tier video game! It really blew my mind. I also use GoLand IDE on there and have managed to get a full day of development done using only about 25-30% battery.

So yeah, whatever Apple is doing, they are doing it right. Performance without all the spyware that your work gives you makes a huge difference too.