I think you need to look at the LOD reading at various speeds - I see 50-60 %power generation a 50-70mph speeds in 5th in the xB which is probably a sweet spot for the engine even though it is turning 3075rpm at 60mph in 5th - not very tall at all. Also being able to climb the max incline allowed at highway speeds is also a factor I am sure.
Too bad there are no values on the X-Y. Graphs can be misleading without actual values.
Yeah knowing the sweet spot in the middle would be nice but I have to believe that it would be the full range say 0 to 6000 rpm would be my guess. Anyone want to spin a engine with an electic motor and measure the torque required to run through the entire rpm range?
1) when accelerating, more throttle at lower RPM can be a good thing = higher load = gets the engine into its most efficient BSFC zone for acceleration.
2) even disregarding (1), once up to top gear the SI tranny is now a penalty. The engine probably still revs away crazily (relatively speaking). If it had a different top ratio, that would be great, but it's probably not as good as the DX gear/FD combination (could be wrong there - I don't know the Honda details).
Perhaps I should say that he believes rpm doesn't matter in acceleration. Anyway, I don't think he's budging on his opinion, I just don't know why he has it, perhaps because it's most convenient for him and wanting a fast car,