Maybe this is a dumb question, but would an HE round in the general area not get the point across?
(I just googled for the ammo types available to the Abrams, and I learned that the latest-version multipurpose HEAT round has a fucking anti-aircraft mode, which enables a proximity fuse and a puff of black smoke on detonation, so you can track your shot WW2 flak-style. I know it's for helicopters, not planes, but still. Crazy.)
At the time, there were only two main gun rounds, APFSDS and HEAT. Both are designed for destroying armored vehicles, and don't really explode like a Hollywood artillery round. APFSDS fires a DU dart at it's target, and HEAT is a shaped charged designed to penetrate armor with a plasma jet.
Same reason people use a shotgun for home defense not a grenade! Limited penetration. much lower required accuracy. If you miss you don't send a shell in a random direction. You can shoot at targets very close to the tank barrel.
(I just googled for the ammo types available to the Abrams, and I learned that the latest-version multipurpose HEAT round has a fucking anti-aircraft mode, which enables a proximity fuse and a puff of black smoke on detonation, so you can track your shot WW2 flak-style. I know it's for helicopters, not planes, but still. Crazy.)