Forgot to mention that the only practical implication would be that defending ground units do not get LBA support (although they could get other hit bonuses like terrain or field fortification)
But you could be right. I've just found this comment in thread Clarification on supplied area:
Rick has ruled many times that in all cases, including even VP counts, supply is only checked on the respective player turn. The non-phasing player is never required to check supply.
If so, it is not correct to talk about OOS defending ground units and LBA in these sentences of rule 3.6, IMHO. This won't happen. Could this be an errata ?