Surely these are not just Debian-owned packages. Whatever Debian decides won’t apply to packages not owned by Debian
So, yes, all those packages are maintained either by an individual Debian Developer or a team of them.
There are third party repos, but they're (currently) neither as widespread nor as commonly-used as those for other major distros. This vote won't affect them, and you might potentially expect to see their use grow if one of the harsher options in this GR were to pass.
If they ban AI, they won't stop packaging apps and libraries from parties that do use AI. They wouldn't even know who does or doesn't.
Proposal C does discourage use more broadly but acknowledges that many upstreams take a different view and that it would be impractical to ban them from using it.