Quantum-based material’s calculations are a simulation activity, because the theory behind these calculations is already known. The postulates of quantum physics, including the Schrödinger equation, are well-known by now so no new theory is created by quantum-based material’s calculations. Therefore it is not a theoretical activity.
I think people have the opposite opinion because they don’t realise the theory behind quantum physics is already well-known. They think solving the Schrödinger equation for example is still part of the theory, but instead you are already simulating certain situations.