I had the impression that the 777 wing was largely not changed, only the folding part is new and will be composite.
The much larger wing span (and aerodynamics on that portion including the tip) help the efficiency of course.
The numbers vs. “competing aircraft” are absurd, especially when you consider its supposedly +16% better than current 777,
saying it is 12% better than 350 is absurd and is likely comparing apples to oranges…
Consensus seems to be that the 777-8X will be somewhat worse vs. equivalent seat 350, although it will have it’s ultra longrange niche.
777-9X doesn’t have any competing aircraft, unless one considers 747-8 😉

Airlines dont’ believe this kind of PR bull****, I don’t see why anybody else should…
Boeing always wants to make things out as a black and white battle of total domination (that they will clean up everything).
Wake me up when that actually happens.