Also, what flavours of Prores will iPhone/iOS support?
(a camera in a walled ecosystem? Would Sony, Canon, et al get away with that?).
You are aware that both Canon and Sony also have their own 'walled ecosystem'? Between using non standard codecs and bespoke media and the inability of some NLEs to see various codecs by both, these are actually more restrictive than ProRes.
While there are better codecs out there compared to ProRes, ProRes has all but been adopted as the industry standard production and intermediate codec.
As for bitrate. Yes, if Lightning hadn't already shown its age, these new iPhone 13s, especially those with large storage, are going to totally embarrass Apple and their belligerence to stick to something that's way past its sell by date and something that is going to massively impede the workflow of anyone shooting video on the 13. There's no excuse for Apple not adopting USB C/Thunderbolt on all their devices now.