Maybe a better way to phrase it is that a report from the investigator could qualify what they considered/found when they said the claims were false, baseless etc, and any evidence they found/data they had access to. (E.g. if they could look at all internal communication but their data retention policy is 6 months and this happened 7 months ago, its not the same as not finding anything)
For example, "allegations of sexual harassment were ignored or not addressed" is a wide range. It could be there were no allegations recorded from the employee (as in, they weren't reported), or they were addressed by a slap on the wrist or a "just don't do that again" to introducing workplace behaviour training, forcing the perpetrator to go through it, suspending them without pay and so on.
You are right it's not proof of no wrongdoing, but it would serve as proof that they handled things in a generally suitable manner, rather than that they managed to twist things around to check a box for the investigator.