I'm guessing you haven't finished listening to the Prime Wardens episode yet? They clarified this later in the episode. He didn't start bearing an egg when they landed on Earth (for some reason), but he did when Plavu'Col was founded, and yeah, by the time the RPG starts he should have a fully mature offspring.
Now, they didn't say what's up with him in the Tactics timeline. He's the last Maerynian there, so he should probably be bearing an egg even as things are coming to a head. The universe will probably end before he lays it, though.