the spar valves would close but fuel could still leak from the manifold prior to the spar valves.
The spar valves are contained
within the wing tanks
Any leaks prior to the spar valve would possibly see fuel flow back into the wing tanks.
The leakage would have occured
after the spar valves, perhaps in the strut area, prior to the fuel pumps and FMU: The FMU has a high pressure shut off valve, so if this was closed, the leakage would have to be between the spar valve and the HP shutoff. Even if the FMU HPSOV was open, the fuel would have a bit of a stuggle to get throught the engine pumps, especially with the tank pumps off and the engines not turning.
Rgds.
NSEU.