On Android no data connection is made, when a connection on the data pins is detected one is offered, but as far as I can tell no device is even detected by the OS until after picking a mode, nothing to attack.

Let me know if I'm missing something, but I get no change in Device Manager/dmesg when plugging my phone in, indicating no data connection to me. It would appear the entire data connection is disabled until a mode is picked.

This is the normal behavior in iOS, and has been for years.

What Apple is doing is _additionally_ disabling the USB port on an even lower level. Currently, the port could still exchange data if it were tricked or hacked, but disabling the port on a controller level will prevent accessing the device entirely.

Or at least that's the theory. Since it can obviously be reconnected after entering a passcode, there are conceivably ways to get it to open up. But that will have to be tested.

Correct me if I'm wrong as I don't have any recent experience with them, but don't iOS devices expose an authentication interface even without unlocked interaction from the user?

Apple's own guide doesn't seem to indicate any form of interaction is needed to enable that interface. That interface is what's attacked by devices like GreyKey if I'm not mistaken. Android devices when not manually unlocked and toggled present no such interface.

Correct, unless you enable adb in developer mode.