Yeah it's called work for hire, if you're employed to do something then you have to agree who gets the copyright before you do the work.

AI art isn't copyrightable because it's the output of a mathematical equation and most sane places decided your can't copyright math - imagine if Microsoft had been able to lock down percentages and no one else was allowed to use them, or of if every bit of electronics had to use sub-optimal voltage values because apple were sitting on a patent blocking people from using the most efficient options.

Copyright was only really invented so the rich can block people from expressing themselves and allow them to manipulate society, it so goes back to when queen Elizabeth decided that her friend should be the only person allowed to make money from salt, a commodity we'd been using for tens of thousands of years at that point. It's all rent seeking and attacks on the poor.