I've been running some tests.
First of all, random note, vehicles apparently do not always appear in the FOW when they get hit. It seems completely random. But just as often they stay invisible. No idea why.

Second of all, a vet 1 Pak 40 does not have a high enough fire rate to manually target a vehicle that got lid up by a previous attack ground shot.
Yes, but it would give him all the information he needed to take a follow up attack ground. The fall of the hit by the little shed there could just be scatter from a shot in the same place, or maybe he assumed that the opponent would back up the T70 after the connecting hit and he adjusted for that, nothing in that clip seems remarkable.