I have just done a test with two different brushless speed controllers to see how the failsafe reacts. In each case I set the throttle to the centre before powering up so the receiver failsafe is set to half throttle. I then got the motor running at full throttle and turned of the transmitter. In each case the receiver took a second or two to recognise the signal was lost then slowed the motor to half speed for a couple of seconds as expected then as soon as the receiver stopped outputting pulses the brushless controller stopped the motor. It rather looks as though the receiver failsafe has little effect when used with a brushless controller at worst it delays the final failsafe by about two seconds.