Transfer speed of USB-C to Lightning on latest iPad Pro 10.5
The iPad Pro 10.5"-inch model supports USB 3, so it is not the "ancient" USB 2 as you mention.

USB-C only refers to the plug, so it hasn't got anything specifically to do with the USB-C to Lighting cable - you can achieve the same, higher speeds using a USB-A port when using a USB 3 compatible cable and USB 3 capable port.