There are lots of things that take out OKW trucks. Lots. What do players do then? They rebuild them.
So why is there so much hate for this ability? Because of the campers. Two or more bases in very close proximity getting rekt by an anti camp ability that comes late in the game.
OKW players want their med HQ next to their Flak HQ, to protect their le.IG's, so that they can forget about them, and let them bomb the enemy all game with impunity. So, the brits have a measure that kills this plan late game, and now the whining starts.
1 truck dead for 325 muni's is a great deal for OKW. It's not the singular truck that is the problem though is it? Nope, despite the protestations to the contrary, it's actually for the very reason I state above.
The problem isn't so much "I'm camping"
The problem is you can deny units being built with one click.
Say you use the ability on a med truck. Healing, I can do without for 3 minutes, but if I need to build a jagdpanzer 4, I have to wait at least 5 minutes before I build the vehicle.
This is even worse with the flak ht, need a Panther? Nope, one click ability delays it for at least 5 minutes (likely longer due to how much schwewer costs fuel wise)
There is no other ability in the game that is able to deny a player from building certain units so easily as Air Superiority.
The only counterplay against this is putting all of your hqs in the base, which goes against core faction design.