WHY is the Belkin Valet charger for iPhone and Apple Watch not compatible with iPhone Xs?

Fix is in iOS 12.1 Beta 3 and 4. Charging of my Xs and Watch Series 4 has been working fine for me. This has been noted in many discussion threads. The public release should be soon as iOS 12.1 is required for the Xr rollout. Surprisingly Belkin makes no acknowledgement of this, perhaps they are waiting for the public release. N.B. There will be a several second lapse between first seating the phone and when charging begins, the phone will initially begin to charge and then stop and start after a few seconds and continue on it's merry way.

Well, given this result from Belkin's website, it's a bit hard to tell what the issue is.