lemme, et al.
Most of the diagrams presented are too simple for this discussion.
Fortunately the aircraft systems were designed to be simple in operation, or as depicted to the crew. Generally you the pilot, had whatever was available / indicated.
If AC1 and AC2 are lost, for whatever reason, then the StBy gen will start automatically; provided it is armed. The crew can override this by manually selecting 'on' or, inappropriately 'off'.
When the StBy generator is running, this section of the green hydraulic system, including hydraulic accumulator, is protected from the rest of the green system.
If the yellow pump fails, then preference is for emergency gear locking and brakes, via the DC pump /accumulator; other services are not available/only available at higher pressures - see engine windmill.
If the green pump has failed then all green services are isolated and unavailable except as for StBy Gen via PTU.
There are a significant number of scenarios for system operation and indication as the engines shut down /fail, but the bottom line is that the crew will have emergency elect instruments, gear free fall and hyd locking, emergency brakes; but probably flapless.
If the gear and flaps were down then more likely this used intermittent pressure from a failing engine or when windmilling at high speed. The engine windmill characteristics involve a relatively fast N1 but slow N2, even to the point of stopping (170kts?).
Hydraulic and elect services require high N2. Normal operations use a flight idle stop.
Flap extension requires elect and hydraulic power. Flap extension takes time, e.g. 0-18, ~ 20 sec.
Without elects, flap position indication is not available, thus crew have to respect airspeed according to the last indication (not selector handle) or the flap position indicated on the wing markings as seen from the cabin (requiring a torch?).
The air brake will 'blow back' towards closed, according to airspeed.
Irrespective of rudder fixed angle or spoiler float, flight control should not be an issue, (some views were that the aircraft was easier to fly without spoilers!). Please avoid the auto systems view 'speed on elevator'; pilots 'fly' an aircraft to achieve an objective, even though the objective may be incorrect.
Some of the calculated speeds appear very slow for what could have been a low or zero flap setting. Thus unless the flaps were selected before all power loss, it would be more consistent speculation to consider stall or near stall conditions.
From deep and failing memory, I recall that the stall warning was available on essential AC and possibly emergency DC.
Other aspects to consider should include resetting/checking the st by altimeter pressure datum, instrument flying accuracy using st by instruments, particularly airspeed ... at night, using emergency lighting.
CAVIAT, any technical inexactitudes above relate to the quest for simplicity; particularly where the simplest view of an accident is often correct.
flynomore; fungus, yes it can, first hand experience of gauging problems, world wide; and corrosion (Columbia!). Also there were reports of possible fuel pump blocking and engines stopping - far east.
Blame implies error or irrational decision and action, for which I prefer more modern views of 'error'.