It's pretty uncommon for a game in development to have its staff pulled off unless something has gone wrong. Most of the time you'll see this for a live service game where content is continually developed. Most of the time it's after a game has shipped, like Anthem developers being moved on to Dragon Age 4.

If a game is lacking content, chances are it was rushed for a release window (ie November for Christmas and Black Friday).

Also regarding the topic, they likely are able to use all the 3d models from Sun and Moon since they were likely made as high poly sculpts. Same goes with reusing animations. My guess is that they wanted to put their foot down here so it'd be less of an issue for future games.