Krastorio 2 introduces new damage types into the game (kr-explosion, radioactive) and sets 100% resistance to this damage types for vanilla walls. AAI Industry adds new wall types into the game (concrete and steel walls) which doesn't have resistance to K2 damage types. As result: K2 railgun turret damages steel walls, but doesn't damage vanilla walls.
Mod adds K2 damage types resistances to AAI walls alike K2 adds resistances to vanilla walls.