Maybe I just missed it, but - what's "natural born", and what's the alternative, in this version of the setting? Most of the Kancolle stuff I've seen exclusively has shipgirls being summoned.
Canonically, Kancolle-as-the-game has summons and "drop ships"
Summons are where humans do a thing, input resources, and get a shipgirl out.
"Drop ships" sometimes happen after battles. No explanation is given, though sometime, for a boss battle, this may be the ship being purified.
Anyway, ignore all that. See the "disregard for canon mechanics" tag up top.
In this case, we have "Manifested" or "Historical" shipgirls, who just kinda... show up. In works where summoning is a thing, this would be referred to as "self-summon." But I didn't want to figure out how people came up with the summoning rituals. This also consumes the hull, so at least the museum shops lent some evidence to convincing people back in the day. None of these are happening today.
We also have natural-born shipgirls, where you take a woman and add thousands of tons of steel until done. "Woke up, am boat. I'm considering selling the rights to Disney."
Also, progress report: writing the sea trials is slow. And also I have three other projects on the table right now.