Never heard that one from any of my trainers. But to be honest, there might be some (very limited) credit to that theory on airbus types. After all, one does not command a control surface deflection, only a g-load command in pitch and a roll rate command in roll. The FBW system takes care of which control surfaces need to be deflected and how much to get the result the pilot wants. And no, no secondary control effects in normal law either.
But in the real world usually two dimensional inputs are needed, so the discussion is rather academic. And even the FBW system in the airbus can't paint over the fact that it is, after all, just a normal airplane, as hard as it tries to do so.