Apple Watch 10 GPS Notify When Left Behind not working

Hi, I have set up my watch and iPhone, to notify me on my watch when I leave my phone behind. My understanding of how it works, and all the information I have studied, is that as soon as you exceed your Bluetooth distance and the phone and watch become disconnected, the watch alerts you. Support have just informed me that it is a feature of the SIM version of the watch! Nowhere in any support documents or Apple set up guidance, does it tell you that it is not available on GPS only watches. I bought the watch specifically for this purpose, having researched that it was a feature, my 14 days are not up, if nobody can help solve this for me, I’ll be returning the watch for a refund. Very disappointed.