Is this an ex cathedra position or is the attempt to harmonize the "incompatible" doctrines? I seek to know, not argue.
There are only certain very limited circumstances in which something is declared "ex cathedra" which guarantees extraordinay infallibility. But all defined dogmas share in the ordinary infallibility of the magisterium which applies to all the doctrines that have always been taught and believed by Catholics. For example, the trinity has never been defined ex cathedra. It's too much a part of normal Catholic dogma to need to be defined in this way. But it is certainly an infallible teaching.