My paternal seventh great grandfather has apparently received Mormon baptism of the dead multiple times attributed to multiple locations after passing away in multiple centuries. I never saw an entry that got it right, out of at least ten. The reason for the interest would be that a branch of the family converted just prior to the Civil War and went west, ending up in Utah. Contact was maintained for at least a hundred years because a few from the Utah branch came to a family reunion in the sixties. All they needed to do was ask. It’s a little insulting to imply that his baptism in life was inadequate somehow, but he’s long gone and it’s of no effect upon him. Even if it was, they missed.
In a nutshell, the work is done by volunteers, it’s part of their religious duty, but it isn’t checked by anyone. It’s basically not valid either from that standpoint or as a database.