S.BUS failsafe and FS_THR_VALUE

I realized that ArduPilot recognizes the sbus failsafe bit, which is good.
Failsafe is set to “hold” in my FrSky receiver.
If I turn off the transmitter, failsafe is recognized by ArduPilot regardless
of the throttle value.

So what is the meaning of FS_THR_VALUE in sbus mode ?
In my understanding it has no effect at all.