Mrdeux...your understanding is correct...thats why the airplane I am familiar with, the B737NG, has separate small battery packs to power these important shutoff valves in the case of a complete power failure.
Islandjumper...my guess is that they were referring to the speed brakes (or spoilers), since the loss of one of the hydraulic systems caused the loss of half the spoiler capability...as demonstrated in the video out the window during the landing.
Cheers,
EW73
