My kickr sends a speed command via bluetooth. I see it in the basic wahoo app and it appears to be pretty accurate based on my pedal RPM.
Zwift’s speed is nowhere near close to what I am doing. If I pedal faster, the speed stays the same. If I slow down quite a bit, the speed stays the same. I have to put my rpm in the mud before Zwift’s calculations make a difference on speed. I dont really care what other people’s speed is, I want to see feedback on the screen based on what I am doing.