If you know where your target is, it can be knocked out.
For example, even in WWII, a german Panther knocked out a Sherman tank he couldn't see. But he could tell where the Sherman was because of the trees the sherman was knocking down as it was moving through the forest. The German tanker was in a position to see the trees falling and was able to figure out the target location. This is from an official WWII era intel report.
So a future tank gun might be able to knock out a tank, shooting through the obstruction, so long as he knows where the target is located.
Some future anti-tank guided missiles actually shoot up into the air and come down to attack the top armor of the target vehicle.
So there are definitley situations when targetting should be allowed, because the firing unit can see a small portion of the target vehicle.
Should a current RPG be able to do that? Heck no! But these rules are intended to be a bit simpler, so there are a few wrinkles. But overall, I think this is a good rule.
TW