I'm not so sure about your second point. He might have set up further back (probably unvoluntarily) so even when he jumped he didn't cross the limit of the grid box. This would also mean that they didn't have any infringement on the rules you posted so they couldn't just give him a penalty.
I remember some years ago it was possible to measure drivers reaction time at the start. I remember Bottas even had an almost impossible reaction of a couple thousands of a second, he probably got lucky but it still was after the reds went out. So how about using clutch release telemetry or wheel speed sensors data and compare that to exactly when they shut the lights? If that difference is anywhere under 0.000, you jumped. It would still be incredibly hard to judge while not allowing any form of movement before the lights are actually out.
Well he was far enough not to trip the transponder
Tripping the transponder is for the amount of movement, not the absolute position. Drivers would park further back and jump start in a way they'd be still behind the white grid marker is it were any other way.
no matter what the camera suggests.
The camera suggested nothing. It showed clearly that the wheel was too far ahead before the red lights were off and section C does not mention the transponder. The stewards made an error by not properly reviewing the evidence, just as they originally noted the wrong incident and later during the race filed a correction. That's it. Mistakes happen, it's too late to apply a penalty. Doesn't mean that we cannot recognize that.
I would honestly be interested about where you got that the transponder is based on movement vs position. And I don't say that to catch you in a lie at all I am thoroughly honestly interested in this and would like to learn more about this tech.
edit: and yes from the in-board cam it does look like at least the contact patch was in-front you are right.
...Just says there's a transponder that's supposed to judge if there was movement. It says nothing about how said transponder achieves that judgement. It doesn't simply senses movement as you astutely pointed out the car very obviously moved. That means it needs a reference point.
So Is it gps? Is it an accelerometer? Is there another sensor on the grid it has to cross? Is it telemetry? Why is there this much wiggle room?