Some flight trainers say that a pilot should separate the inputs on both axes, doing only one-dimensional inputs, i.e. pitch or roll inputs, but not at the same time.
Apollo, I'm a bit old and thick and worse still an ex-trainer ( basic jet) but I'm struggling to reconcile that statement with landing pretty much any type, big or small, using the "crab" technique in a crosswind - where in the final moments you need (hopefully) co-ordinated inputs of roll, elevator and rudder all at the same time.
I would agree with the sentiments of +TSRA when he says
I would suggest those instructors go rent a Cessna and re-learn how to fly because that is the most useless statement on training I have ever heard.