this is actually all about TSMC N3 and the problems they've been having getting it to work and yield. N3 itself is essentially canceled and split into two node

this is actually all about TSMC N3 and the problems they've been having getting it to work and yield. N3 itself is essentially canceled and split into two nodes: N3B (b for Bad), which has a small gain, and then N3E (E for Enhanced) which comes next year with the performance that was originally promised for N3 (now N3B). N3E is not design-compatible with N3B, and will yield better at lower cost (because they're replacing some DUV layers with EUV) once it's finally running. In theory. So basically this year they are releasing the A17 Pro on N3B, and the base-model phones get the old A16 (which does not have native USB3). Then probably next year they release A17 Bionic and update the base tier phones. It's also highly likely that the A17 Pro itself gets refreshed, since it will be lower cost on N3E (and this matters at Apple's scale, the validation/testing costs are worth it). And that's the point when they'll start doing M3 chips in laptops too, most likely - actually some analysts thought M3 non-Pro/Max was a possibility (smaller dies/higher yields) but I guess N3B yields are that bad.