RAT, you are correct, thats' why we set the speed according to the lowest "indicated" to give the safety margin. The point is system diagnosis. If the F1 bug appears it means the signal has been sent from the lever to the actuator and the bug appears. If the pitch changes in level flight with fixed power it means "something has moved" . If there is no "transit light" it means they are in "commanded position" . Of course there is always possibility of multiple complex failures, but unlikely and the QRH has "flaps up landing" if there is any doubt. Once the "eyebrows appear" we have another clue.. as Mr Boeing advises..time spent on diagnosis is rarely wasted and the QRH assumes the flight controls are in the normal positions for the phase of flight. The alternate flap extension system is completely independent and locks out the hydraulic fuse as a fail safe. There is something missing if we can't diagnose how much flap we have..But in cloud, at night, with NO light indications it would be worth levelling off and spending 10 mins investigating.