Thanks for the links, @[deleted]! 🙂 (And welcome, fellow programmer! ^_^ May I ask where you're from?)
I think I would classify this as a "missing feature" XD
I'm actually hoping to avoid SSO, if possible, since it can be kind of awkward at times (for example, completely logging out of an SSO system usually involves redirecting one's browser between multiple logout pages, and if there's a network issue, then one ends up being only partially logged out, which is kind of awkward).
I'm thinking that the best solution will probably be to either modify the core Flarum code so that it directly uses the My Little Word Land users
table or to generate a view in the database so that Flarum thinks it's interacting with its own users table but it's actually using the My Little Word Land one 🙂