I just mean that these behaviors can be highly subjective. Often, I open the rear door to let my son in first. I want the screen and climate controls to be on immediately so that by the time I sit down it's ready to roll.
The seat sensors might not be on until the computer is on, at which point everything else is on. There could be a lot of hairy workarounds in the software to make it behave like you want it to, and that might not even be desirable to most other owners.
I'd say opening the door again and again without getting in is a very small edge case. You could always turn off the climate and music while cleaning the car.
The whole idea is that things are as automated as they can be (it's not perfect, but that's the idea). You walk up, open the door, get in and drive away... no unlocking the door, no ignition... and the same on the way out - you can just pull up, open the door and walk away (no park, no ignition, no locking the doors).
There's the "principle of least astonishment"... that everything turns on when you open the door makes a lot of sense. Everything turning on when you sit in the seat is less expected behavior in my opinion. Keep it simple.