You have also been misled about Ryanair's fuel league tables which rank only fuel burn per month and not fuel loads per flight. The sole purpose of these tables is to encourage pilots to fly safely (i.e. at the correct heights and speeds), they do not rank fuel loads or extra fuel taken.
How does that work then? I thought ultimately the Boeing perf figures would give you the best FL and speeds, not to mention the FMC. What am I missing that a fuel league table would add?