I think S-signatures were meant to be a legal concept to make “electronically signed” documents by some other means, much less contestable in court. It’s not that “/s/ John Doe” is more secure. It’s that there’s statutes and precedents behind its practice that a court would accept and lawyers are less likely to challenge.
Having a signed document, with an ink signature, can still be challenged in court, for example, but would require something like an expert witness to show that it’s fake. Whereby, the automatic assumption of the court is that an ink signature is valid. The same would be true of a S-signature, as everyone has been electronically submitting court documents in this way for years (not just federal Courts, but Texas Courts).
The wiki’s authentication system on the other hand (managed by volunteers, which may or may not be reliably audited, and who might have a conflict of interest) would be a soft spot for an attorney to focus their attack.
An attorney who focuses an attack on a S-signature, on the other hand, would likely bring on the wrath of the Court.