Well, first of all thanks for the advice about precision.
But reading the FCOM precisely, did you find anywhere stated that when the center tank pumps operate the inners receive fuel from the center tank? I thought in that case center tank is feeding the engines and not the inners. Part of engine fuel is returned to the inners via the outers.
Why turning center tank pumps off at the beginning of the investigation process is crystal clear.
If this process leads to the conclusion that center tank is leaking (inners deplete at the same rate), it would make only sense if center tank had a certain amount of fuel. Center tank being not empty the inners quantity would be between 4.9t and 5.4t each at the beginning of the investigation process. Suppose crew is so slow that it needed 30 minutes to investigate, fuel burn from the inners during investigation and while center tank pumps off, would be about 1.2 t total. This would leave the inners with about 4.3 to 4.8t each. So again, why wait for 3t and not use immediately whatever is left in the center tank?
And suppose you do end up with 3t in either inner, you still think that you can top up your inners from a leaking center tank? That' s a total of 4.8t needed from the fuel return valves
And how am I supposed to find it out if this is possible in a normal flight if not by switching off the center tank pumps off and wait the inners to drop to 3t ? Not a good idea, is it.
And by the way, not my inners but your fuel flow is bigger than usual.