Yeah I'm not saying bluesky is growing because of their logo:). (Although they have just branded with the butterfly, which will undoubtedly be in the link button thingums).
You could argue that nostr would also have the 'jack effect' but that doesn't seem to be the case or not nearly as much(?). I think something more is going on with bluesky. I think it's more significantly been adopted (and gatekept - if that's even a word lol) by the lgbtq community Elon exodusers, who actually also seem to dislike jack. Much in the same way nostr is predominantly a very particular community - bitcoin twitter offshoot, but this is far more of a niche. Anyway, yeah. I can see 'powered by Nostr' being a thing too¯\_(ツ)_/¯