The article focuses on games that were never released or never even completed. It could be argued that those (unlike Pac-Man) did not contribute to cultural heritage. This is obviously not to say that their preservation is unimportant; I just think it should be compared more to unfinished/unpublished works of art, not the statue of David. It's more like The Salmon of Doubt than it is The Hitchhiker’s Guide to the Galaxy.
You're right. My comparison was more about sculptures as art vs the games as art. If you don't believe them to be equivalent at some level, it would be difficult to find this preservation work worthwhile.
That said, unfinished games are similar to manuscripts of an unfinished book. Many such manuscripts have been published throughout history and are, in my opinion, part of our cultural heritage too.