That may be so, but I really doubt there is much coherence. Almost all ex-Scientologists hate the Church of Scientology. That's common. Probably most ex-Scientologists have no use for Hubbard's "tech". But that's not much for a "movement".
Let me explain. There is little agreement on how important being anti-Scientology is. Most don't really care and have relegated Scientology to the past -- best forgotten.
But as for "something better", few (I believe) have any interest in "improving" Scientology. For almost all, it's simply not worth it. If there were any noticeable results, that might be different, but with no reliable or significant results, it's a dead-end. A proven dead-end.
I don't see enough agreement to call it a "movement".