You are confusing two different things. Cumulatively a 12 gauge bird shot shell has considerably more energy at the muzzle than any handgun round and most rifle rounds, yes. But when those pellets hit the target its notnthe cumulative energy that matters butbthe individual energy of each pellet. If you glom all the pellets together with wax or another binding agent then they add all their energy together, for as long as they stay together.Point taken. I know they don't penetrate enough. But the emoji poster is saying that birdshot doesn't have more energy than a handgun bullet because each pellet has a miniscule amount and together they don't add up.
Put a 9mm point blank at gel and then do the same with birdshot. Tell me which one flips over the block.