In this case, the camera package they linked to is being developed by the Flutter team, so... the quality controls are surely in line with the core library. Having it outside the core offers a number of benefits, as I mentioned.
Tim Sneath linked to the official plugins list in another comment, https://github.com/flutter/plugins, and both camera, sensors and connectivity, would be akin to the kind of ownership I'd expect. It's definitely a good start.