One could also say "P4 should not be able to repair on the frontline and bounce AP shots in a row. The P4 shouldn't be in a position to be hit by the AT gun".
This is pure bad RNG, but still, that's not an argument that holds water, that these are different scenarios.
The P4 repairing isnt relevant to it bouncing shots/being on the frontline though. It would/could have been taking that fire without the Sturms repairing it, and it would have made no functional difference to the situation. Unless you're suggesting tanks being repaired should have an increased vulnerability to AT fire, though that's a totally seperate subject.
Medium tanks are expected to be on/near the frontlines and to receive fire from AT guns, this interaction is expected throughout the game, in pretty much all medium-based engagements.
Conversely; Tank Destroyers shouldn't be taking return fire from the mediums they're attacking unless you've made a massive mistake. TDs outrange mediums and so they dictate terms. AT guns similarly outrange Mediums.
They're entirely different scenarios even if you're wanting to invent a really contrived reason they aren't.
Show me a map where you're always have max range advantage with your Jackson, except Steppe en 4vs4, there are none, True is map are designed so max range is difficult to use.
P4j have advantage on Sherman, which make the Jackson only reliable counter to P4j. Your examples are about a unit that face a vehicle from a different category and as I stated I'd agree with the situation if I were facing a heavy tank but here it is just the usual medium tank.
And M1 isn't the best Atgun in game and even if, that's doesn't make it an argument since its facing much higher armor.
Which maps are in the rotation that have no access to 41-60 range overlooks? You can use the Jackson's range advantage against a P4 in pretty much any realistic scenario you'd want to.
The P4j isnt an "usual" medium tank. It's the latest-arriving and highest-cost medium going.
The M1 is arguably one of the best AT guns going, the range/vision advantage alone is a massive boon. The main downside of the thing is the constant muni investment. The ZiS and PAK-40 can certainly be argued to be on-par with it though.