I would say that the in-group jargon is more of a retention tactic than an attraction tactic, although it can become that for people who are desperately looking for an ordered view of the world. Certainly I've seen it a lot in recovering Scientologists, expressing how that edifice of jargon, colloquialisms, and redefined words shaped their worldview and how they related to other people. In this case here, if you've been nodding along for a while and want to continue to be one of the cool guys, how could you not glomarize? Peek coolly out from beneath your fedora and neither confirm nor deny?
I will agree that the ratsphere has softer boundaries and is not particularly competently managed as a cult. As you allude to, too, there isn't a clear induction ritual or psychological turning point, just a mass of material that you're supposed to absorb and internalize over a necessarily lengthy stretch of time. Hence the most clearly identifiable cults are splinter groups.
There's maybe still a concise social history to be written of how all this crap congealed together. I'm particularly interested in the overlap between the AI doomers, the ancap libertarian weirdos who wanted to nail down their economics as capital-S Science™, and even the online poker grinders of the 2000s who aspired to become statistical-thinking robots. I hesitate to say any of this is undocumented, because the reams of posts are still out there, but a Michael Lewis-style pop history of it all would be a hoot. I understand Elizabeth Sandifer has it all well-covered from the ideological angle, and Adam Becker's new book looks good too, but having something covering it from the forum/feed-poster angle might end up being the epitaph the movement deserves.