Thta was my guess, but that requires (see my edited post, sorry, I had not fleshed out one of the later thoughts) a significant churn of a very expensive engine, times four.
I admit to being in the dark. I'd have expected a new/recent generation engine to have a thousands (1,2,3, more?) of hours on wing, not hundreds of hours on wing, requirement to meet a long haul carrier's requirements when engines are proposed as the powerplant for a long haul airframe.
I should just have said that, perhaps.
If that idea is half cocked, or just plain wrong, please advise.
Since I have far more "hands on" with turboshaft engines than with turbofan engines, I may be missing a fundamental point.