TURIN;
With a dual engine failure is it assumed that there is limited AC electrics available?
RAT? PTU? etc.
Perhaps. I suspect that the minimum 150kts speed recommended is to stay above the 140kt minimum speed for RAT operation (after loss of AC1 and AC2. The RAT does power the blue system which then provides some electrical power through the Emergency Generator.
Also, a windmilling engine may be able to develop some hydraulic and electrical power at higher windmillling speeds, but again there is nothing definitive that I can find on just what is available, even anectdotally and not by test or certification.
Perhaps the answer lies in the fact that only the blue hydraulic system is powered, (by the RAT under a dual engine failure) and that is all that can be said, but the actual airplane may be able to provide more than this minimum. Still, nothing about the yellow pump...