What I'm contending is if the assets are actually free. And just because they were all created by volunteers and contain no data from the originals doesn't mean that they are actually free. The rules around derived works are complicated, and too close homages have been found to be derived works, even if there is no actual copying.

If this were to go into court, things that would matter would include both "how visually similar do they look" (the answer is "very"), and "was the artist aware of and did they refer to the originals while doing their work", (given it was done by volunteers who are enthusiasts of the original game, the answers are almost certainly "yes" and "they can't prove they didn't").

And on those facts, the new art is a derived work of the original and falls under its copyright.

Forgot to reply to this part: And the reason those clones exist is because multiple companies reimplemented the BIOS in a clean way, where they had one team produce a clean spec of all the interfaces, and then sequestered a different team, who could attest in court that they had never worked with, seen or in other way come in contact with materials related to the IBM PC, to produce a replacement BIOS based on only the given spec. The clone makers that didn't go to all this effort were sued out of existence.

Do you believe that the free assets produced for games generally meet this standard?