Is the claim about rational incoherence?  Then it would seem to be  the claim that the only kind of practical, rational incoherence is  instrumental incoherence.  But this claim would have to contend with the  idea that there are other kinds of practical, rational incoherence.   For example, it seems incoherent to refuse to intend what one believes  one ought to intend.  It also seems incoherent to intend to X and to  intend to Y when one believes that if one Xs, one will not Y.