thats proven by the fact that on occasion the 250f class posts lap times very close to the 450s
Exactly. I think KTM's 350 SXF idea has huge potential, the just need to drop the 250F powerband and make it a 450 powerband. If they do that, focus all the power in the 6-10 grand range and put the rev limiter at 11 odd grand like most 450s, they would have a supercross weapon.
Considering the sx350F makes roughly the same amount of power as 250 two strokes when in the same rev ranges, and no rider no matter how good can use all of their factory 450s power on a modern supercross track, plus the handling and braking advantages of a two stroke, its not hard to see it happening with the right rider.