I disagree.
In magnetic-coupled inductor each coil cover the total magnetic flux generated by the two windings. With the same number of turns and the same volt-seconds applied to the windings, the total magnetic flux is equal to twice the single-coil magnetic flux.
Therefore, based on a common definition of inductance L = dPhi / dI, where dPhi - the magnetic flux covered by the turns of the winding, dI - change in current in the coil, the equivalent inductance value of each winding in magnetic-coupled inductor is equal to twice the inductance of a single coil.