Energy is energy. The 5.56x45mm at closer distances, has less. Energy is used to turn a bullet into penetration, expansion, and fragmentation. Now, you claim that pushing pieces of metal through living tissue "is incidental rather than the wounding mechanism". I'm pretty sure putting a broadhead arrow through a deer's lungs transmits almost no pressure wave, yet that deer will be deader than Elvis.
I'm going to agree that rapidly transmitting shock to the body is destructive, but disagree that your newfangled .250-3000 is a death ray, and can be used on any game, no matter how large, because it's so destructive.
Yes, a high velocity round has been around for over 100 years. The US government didn't adopt it as its primary rifle round. It doesn't do a good job on game larger than deer- why? Because your magic pressure wave is just one part of the effectiveness formula, not the "(primary) wounding mechanism".
Sure, speed does kill. But only when intelligently combined with the wounding mechanisms of penetration, expansion, and fragmentation, to go with that shock.
John