I used the same method with my students. I told them to leave the card alone. This is because if you forget to turn the card one time your reading the wrong bearings. I always taught to just use it as a poor man's RMI. Where you just visually put the neddle on your DI. In a high workload of IFR it's just another distration when your a student. This was FAA IR's though not sure about the IMC because I've never done one. That maybe what your instructor is eludeing to.