Plane: neurotic throttle behavior

[robustini]

FPV model without real airspeed sensor, TECS synthetic airspeed enabled.
The CTUN.Tho in the first part in Cruise is without a real airspeed declared, so ARSPD_TYPE 0, in the second Cruise is with ARSPD_TYPE at 2 (Ardupilot default), although obviously there is no real analog airspeed sensor in the plane.
Our wiki obviously says to put that parameter to 0 but then you have this absurd throttle behavior.
In order to have a smooth throttle i think it is not normal to have to declare a non-existent analog airspeed sensor and leaving it unused.
Perhaps imho it would be more logical to have an option in ARSPD_TYPE that targets the synthetic without having to declare a sensor not installed, or that anyway setting it to 0 doesn't then have the motor seem to go crazy performing unwanted RPM variations, my two cents.
Log available, but the same thing is reproducible on SITL in an instant.