I think some of it is personal, like "oh, I don't like that developer or that group, so I won't move until my favorite builds something", but that's actually a Nostr anti-pattern.

This is an open protocol. Anything you move will be visible in any later app, or could be easily migrated to a new event kind because json is structured data. The first dev is just helping you work out an example implementation that does *something like this*.

You don't have to marry them, just help them build their app.