I don't think this means "most concerns aren't valid", it's more "people aren't always good at vocalizing their underlying concerns, and instead treat a proposed solution as the concern".
Your distinction between stated concerns and underlying concerns is a red herring.
If their underlying concern is "our wiki will be full of inaccurate info because the wiki is open", and if that's empirically shown that opening the wiki doesn't produce a wiki full of inaccurate info, then it's an invalid concern. Neither it (the "underlying concern") nor the stated concern are valid.
You're not engaging with the premise. There is no problem involving a wiki that is full of junk and that locking it down is a way to solve that. The concern is that it would be filled with junk if flipped from closed to open.
If their underlying concern is "our wiki will be full of inaccurate info because the wiki is open", and if that's empirically shown that opening the wiki doesn't produce a wiki full of inaccurate info, then it's an invalid concern. Neither it (the "underlying concern") nor the stated concern are valid.