That whould make sense, but what about the few latest fleets like macross 11-15 that where launched after the VF-19 was approved as new main variable fighter, whouldn't those fleets have the 19 already ? what whould be the point in build a fleet from scratches and equip it with fighters already out of date ?
Note, I haven't played any of the VF-X games where, from what I understand, you face M13 which has been hijacket (how lol ??). Maybe it has been stated or something there, I don't know.