lobste.rs is invite only which makes it hard for people like me to sign up

Yep, but my guess is that Lobsters is probably around 1/100th the size of HN on any dimension you care to measure (some recent stats: https://lobste.rs/s/8yumgi/killed_by_google#c_ugdtol). We explicitly have a narrower scope and are not interested in trying to dethrone/replace/etc HN. But ultimately, "split" is too vague a prediction to be judged as accurate or inaccurate.

(Context: I am the admin of Lobsters.)