OK. I've tried multiple coax and optical in both the Wiim Pro and a RPi4b with a Digione hat using Ropieee.
All of the cables achieved 24/196 on the RPi. None did on the Wiim. My conclusion is the the Wiim Pro cannot achieve 24/196. Either all the responders here are paid by Wiim to say it does or you are all unable to judge 24/'196 on your equipment.
I couldn't be bothered to send it back but ebay will do.
Shame on Wiim.