Facts are usually supported by evidence.
If the flow is really working and an incentive then why wouldn’t the company want to highlight that? Don’t you think the names and class dates would be published in that ridiculous “wings and things” newsletter or at least something on the FB page.
These “facts” are coming from a recruiter, who’s job it is to fill seats by whatever means necessary. I’m sure they aren’t lying exactly, but maybe not being completely honest either.

Kind of like me telling a girl she could become a model if she lets me take nude pictures of her. Is it possible? Sure, why not? But it’s about as likely as GoJet new hire flowing to Spirit in 2 years.