The only purpose of the 6.5x284 was to shoot very long high-BC match bullets of the type used for minimizing wind deflection at 600 and 1000 yards.
No comparable match bullets were made in .257, .277, or .284. They were and are made in .308 but to get the same wind deflection abilities as a 142 grain 6.5 bullet you would need a 230 grain .308 bullet of the same shape and velocity. That's a major PITA for recoil and other reasons, which is why most .308 match bullets are 155 to 200 grains, which aren't as good and still recoil a lot.
A 6.5-06 would work as well in this regard as a 6.5-284. The latter, though, follows the "short fat" philosophy which gives a a slight accuracy advantage. This is why the 6.5-284 is popular for 1000-yard target shooting. Bear in mind that for 1000 yard target shooting, you don't care about foot pounds of energy, the target never moves, you always know the range exactly (it's the same as the last time you shot), and you get two sighter shots.
None of this has anything to do with hunting and there are many good hunting bullets in .257, .270, .284, .308, etc. That's why the 6.5-284 offers little if any difference for hunting.
