I would think so too - can't marge individual NNs.
We don't know that. It is possible there is only one set of NNs that is being cross compiled on all HW versions.
Otherwise - not sure how he shadow mode would work (or gathering data ?).
ps : Essentially, if we want to say there is a very different FSD dev branch that hasn't been merged with production branch, we need to reconcile that with the fact that hacked production branch has autonomy day demo features and show how shadow mode is supposed to work. Also, that would mean there is a separate development effort going on with the production branch (!) since the software is obviously improving. And, they have to retrofit all production branch changes into dev branch changes. I can assure you I've done all these crazy things
Occam's razor says, they are doing the simplest thing. Create dev branches for individual features and merge them back once dev is done.