No matter what CPU you have, if there is a piece of software that refuses to go sleep, the battery will be drained anyway. Core M wont magically fix Chrome's shitty codes.
That's like saying "lets install 2L engine on a Hummer". The efficient 2L engine wont magically make the Hummer any lighter or less of a burden to move. You still need to somehow make the Hummer lighter.
That's what I have right now... 0.6% per hour on average, no hibernation. The difference between mine and the stock configuration is merely the hibernation which IMO is highly unnecessary since its already efficient on the first place. I didn't tweak, I didn't change the system config apart from disabling hibernation. Just stock. I just don't use shitty software like Chrome.
But I can understand the reason behind the 4-hour hibernation: to make it foolproof and ready for shitty software.