It's done over USB 2.0 largely because that's simpler than involving newer and faster specs, and partly because that's how the original iPhone did it.
My understanding is that all complaint USB USB-C cables should work for USB 2.0, even USB4/TB4 cables, but active TB3 cables might not hook up the USB 2.0 pins.
My understanding is that all complaint USB USB-C cables should work for USB 2.0, even USB4/TB4 cables, but active TB3 cables might not hook up the USB 2.0 pins.