Cortisol drops the longer you're awake. And we don't want to eat when cortisol is high. So the later we eat and spike our insulin. the lower our cortisol will be, the better.
I'd make it dependent on when you go to bed with the carb backloading. Would try to not eat like 4h before going to bed(brainhealth reasons).

Short and simple, high cortisol(high lipolysis) = high fatburning , so long food not available, high concentration of your fat gets burned
High cortisol + high insulin = your food you take in gets used suddenly into high fatstorage
That's the really short version, there's tons of other things going on with oxidative stress, fixing and balancing cortisol levels and other weird shiet when eating high carb during specific times.

The mainfocus should be probably to not eat pre 1pm, from then on cortisol is already significantly lower compared to all the hours earlier. But keeps steadily dropping till like 3am.