I've noticed that there's a weird tendency for anti vehicle weapons, but less often anti infantry ranged weapons, to get the Concussive tag. What the bork?

Someone on these forums made an off handed reference to them applying to vehicle crews when struck. This reminds me of the "crew shaken" "crew stunned" results. Should krak grenades, battle cannons, etc. stun the crew of a tank?

Certainly gives a better use for Iron Jaw and such for tank crews, and gives ork and maybe CSM crew a slight edge.

It's incredibly useful against vehicles. Stun the crew and take that extra pit of time to close the distance, or plant a meltabomb on the rear armour, or board the enemy.

RAW, no, I don't think it does anything against vehicles. It's more for those characters that have the temerity to survive a hit from anti-vehicle weaponry.

In my game, we've been running that yes, Concussive can shock a tank crew. The 'nice' way of running it like this is to grant the crew a bonus to the Toughness test equal to the armor on the tank facing taking the attack, similar to vehicles taking Flame attacks.