That’s my take on it. Great for some stuff, not for others. Definitely any complex chords, we need curvature to not mute the other strings in the chord. I do think for single note playing flatter fingers are useful. Eric Johnson uses very flat fingers for his solos, yet his bends/vibrato are among the best in the business. I’d have to check his playing and see how he negotiates the change required when bends come up.
Pulloffs…yeah. That’s gonna be hard. The “all hammers” legato technique that Marshall Harrison, Rick Graham et al use…probably possible and we’d get the needed dampening help that comes from flat fingers that’s so important. In this videos, I’d say Marshall’s fingers look pretty flat:
But, I guess that’s where the technical mumbo jumbo comes in, because I’d call this flat relative to the curved fingers classical guitarists have to use in the bulk of their playing. Maybe to someone else, Marshall’s fingers don’t look flat at all.
Same thing here, Rick’s fingers look flat-ish to me,
but that’s just “relatively” speaking. I don’t know I’ve ever seen anyone play with their fingers completely “straight” so, I don’t know how flat we’re talking here. The above 2 monsters don’t use what I’d call “curved” fingers though.
At any rate, there’s probably going to be very few times anything is useful in all situations.