one needs to check the drift angle between ILS FC and aircraft's kinetic vector e.g track as it's simple logic. If you have the correct DA then de-crab isn't a issue in case the aircraft believes to have it's vector aligned with CL but's not you end up like SQ in MUC. Aircraft will try to to align it's ground track with the CL and guess where you'll end up with the ground track diverging more than 5 degrees.
