That's fine, but not the primary issue.

At some point these companies will need to get licenses for any copyrighted work that was part of the training data, or start over with public domain works only. The art may be data, but that data has legal owners whose rights grant control over it's use.

Another way to think about is proprietary code. You can see it and learn from it at your leisure. But to use it commercially requires a license, one that clearly defines what can and cannot be done with it, as well as fair compensation.