That's an interesting point but it's just a part of a whole situation. Boeing might recommend to retract flaps from 30 to 25 but I'm quite sure IAS control and initiating a best-glide speed recovery will be the priority once the lack of thrust is being confirmed.
To understand this simply imagine that you're already configured flaps 25 when the failure occurs: speed control is obviously the most important task to perform.
Once again I'd be very interested to know what prevented the PF to revert to best glide speed earlier, at least once flaps 25 were selected. The fact that manual speed control was only initiated when the stick-shaker got activated looks like a passive and not an active decision. Why? Retracting flaps was one thing but speed monitoring and control should have remained the priority. What interfered?