I'm pretty sure if a copyright owner dies without heirs the copyright is orphaned, it doesn't become state property in the US. That's the problem. If the work became public domain it would make more sense.
That's the sort of provision that is effectively unenforced, and is hence null in practice. I expect most states do not know whether they own any IP from dissolved companies, nor will they prosecute anyone who "infringes" such rights.
Ignorance of the law is no defense against prosecution, and any claim that "it's null in practice" is about as bad legal advise as you can give.
Even if the company went bust, and the former owners died, and they have no legal heirs, that copyright is STILL active and now lies with the state, whether the state knows that or not.
It might be called an orphan work, and it might take a whole lot of digging to discover it's now owned by the state, but it is owned, and they do have the right to prosecute over infringement if someone at any point goes "hang on, we own this, and we can make close to 50% of our annual budget by prosecuting".
