> According to the dictionary, morality is simply “ principles concerning the distinction between right and wrong or good and bad behavior.”
Right/wrong in this case are meant in the sense of "it's wrong to murder people" as opposed to "saying 2 + 2 = 5 is wrong." The former is a statement of morality, the latter is a statement of correctness. This does not link productivity / morality.
> Some would say that choosing being unproductive when you could be productive IS immoral.
Therefore it's not an axiom. Most people would only consider it immoral if you chose to be unproductive for the sake of being unproductive. For example, refusing to do your job while expecting to be paid is something many people would consider immoral.
This is different from choosing a path you prefer, that happens to be less productive. For example, doing something more slowly but more safely may be less productive but also something many would not consider immoral.