It's probably pricing out XXX-LHR in M12E then collecting the surcharge for the F segment LAX-FRA. Basically doing a paid, one-segment upgrade from Y to F at the point of ticketing.
In the fare breakdown, it will have an additional item for the additional collection to book in F as well as the M12E XXX-LHR.
I never once thought that US$10,000 for one transatlantic ticket could be considered an "AMAZING price", though. Shows how much I know
