FTMS client doesn't change rolling/wind resistance data

Similar to the other post - apologies if this isn’t the correct forum.

I have an FTMS service that is getting simulated bike data, but the only thing that changes in the grade. The other three values are constant - wind = 0, Crr = 0.004, Cw = 0.51.

This seems wrong. When riding I can see that for the same wattage/grade I get a lower speed on dirt paths versus paved (for routes like Serpentine 8 or Jungle circuit where you go on/off road). So obviously the Crr is changing in Zwift but not being updated in the FTMS Control Point characteristic with the 0x11 Simualted Bike Data OpCode.