Part and parcel with producing for TV is brainstorming a bunch of show pitches, and most of those are throwaways. You toss them out there and see what sticks. I bet this was just one of many Roddenberry concocted trying to get a network to bite.
Hmm, maybe that's why it had a name as generic as Starship. Maybe that was just a more convenient way of saying Untitled Starship Series, and if some network had bitten, he'd have come up with a better title for it.
(Admittedly, Planet Earth is an even more generic title, but that was a retool after he couldn't call it Genesis II anymore.)