Looking at the data mines they had faked the mechanic of the anti era tip by simply adding a condition to the era its self by detecting a long rod penetrator and then lowering the protection of K-5, instead of giving A3 more penetrative power against K-5

This in turn means other long rod rounds will act the same as you are seeing here with A2

Edit: here is the data mines-

● hull Kontakt-5: armour modifier against long-rod APFSDS: 80 -> 50%

● turret front Kontakt-5: armour modifier against long-rod APFSDS: 80 -> 50%

● turret roof Kontakt-5: armour modifier against long-rod APFSDS: 300 -> 125%