My ADSL speed is lousy, so when I need more bandwidth I tether a mobile phone to the router's Ethernet WAN port to provide faster access via 4G.

I'd been using an Android phone connected to a Raspberry PI USB port with the Ethernet port on the PI then connected to the Ethernet WAN port on the router. Set up bridge-utils on the PI and it works perfectly.

I swapped to an iPhone, and this didn't work, because the Android phone appeared on the PI as a USB device and the iPhone appears as an Ethernet device. Added the iPhone Ethernet device to the bridge-utils configuration and that works.

But it would be great if it was possible just to connect a phone's USB port to the router's USB port and have the phone appear as a device.

I came across this https://www.visus.pt/mirrors/draytek/tools/iPhone%20Utility/Internet%20backupsharing%20by%20iPhone%203G3Gs.pdf which suggests that once upon a time, it was possible, but on testing I couldn't get this to work.
It would be great if there is an up-to-date version of this; am I correct in understanding that there's not?