How quickly can guys be expected to react? With training and awareness it could be done fairly quickly. How quick does a trained pilot apply rudder with an engine failure?
This is certainly why Boeing issued recommendations on monitoring automated approaches which insists on mandatory manual override as soon as an automatism default is identified.
Retracting flaps from 30 to 25 improves the aircraft L/D "global" configuration, but you still need to fly the right speed to get the best of this new configuration. Flying best L/D speed at flaps 30 will take you further than flying minimum speed with flaps 25.
It's exactly like on a go-around: retracting flaps is improving the aircraft global aircraft config but you still need to fly the right speed to get the best GA performances.
In this particular case the captain's decision to retract flaps reduced the poor gliding performances resulting from flying at minimum speed.
The report clearly demonstrate that it was better than doing nothing, but it sadly fails to show what would have been the benefits of controlling the airspeed.