As someone involved in engineering boards with both USB 2.0 and 3.0 the costs are negligible. You're not wrong about more traces or about it requiring more attention but per phone this cost less then a few cents.

I think it's more about the upsell to the Pro line or as you suggested encouraging use of iCloud.

[–] jasondj@ttrpg.network 1 points 1 year ago

As I remember it the USB 3.0 chips can cause interference in 2.4GHz range unless shielding is used and the USB chipset is kept far away from the 2.4Ghz antennas. Probably just “juice not worth the squeeze” on the smaller non-pro model, if there’s a significant chance it could interfere with Bluetooth and wifi.