I misspoke in my first comment. It's vague on if copyrights are shared but it does explicitly say it gains ownership.
In any case, this issue has been brought up and they haven't fixed it. Every other platforms makes it very clear who has ownership of what. There's too much room for abuse and its either a grift or incompetence and with all the other problems with the platform, it's not a good look.
Federated platforms are popping up for this kind of thing, better to wait imo.