It is not a proprietary cable. It is a 5 meter long USB-C cable capable of 3A (it doesn't say the wattage, but Quest 2 uses QC 3.0 which is 18W) which does 5gbps data as well. It is an active fiber optic cable which is necessary because the USB 3.1 gen 1 (5gbps) spec doesn't allow for passive cables over 2 meters.

* https://www.usb.org/sites/default/files/USB%20Type-C%20Spec%...