Cannot understand the mechanism of VTOL GCS failsafe


in above page, there is the phrase

“Enabling this option opens up the possibility of your plane going into failsafe mode and running the motor on the ground if it loses contact with your ground station.”

I couldn’t understand this meaning.

with arducopter, if I turn off transmitter or ground station while the copter is on ground.

there was no problem on this behaviour.

in the above page the phrase is too ambigous and I cannot understand what the specific situation that will cause this motor spinning.