GG
Not wanting to muddy the waters too much here, but the 737NG NNC for 'Landing Gear will not move up after Takeoff' specifies-
"Note: Do not use FMC fuel predictions"
That is before actioning any of the checklist items!
I suspect it may have some importance!
I know Airbus do things differently (or is it Boeing) but I would wager that there are some common areas where all pilots regardless of caste will come unstuck!
Perhaps LFF was not specific enough.