Correct, contingency fuel is for unexpected contingencies. .For most airlines this is around 2%, which leaves a 7% deficit. For a -400 LAX-LHR that adds up to an additional 9000kg burn assuming no dawdling or holding. What doesn''t add up?
What doesn't add up? Your assumption that most airlines carry around 2% contingency for a start.
Try reading the surfeit of postings on the subject (this and the previous thread). Distill the facts from the speculation and you will quickly realise why many of us groaned when you started pontificating.
Quite what relevance crossing the Atlantic as few as 20 times per year has is also puzzling.