That sounds like a less serious problem—if the tool highlights the allegedly plagarized sections, at worst the author can conclusively prove it false with no additional research (though that burden should instead be on the tool’s user, of course). So it’s at least possible to use the tool to get meaningful results.

On the other hand, an opaque LLM detector that just prints “that was from an LLM, methinks” (and not e.g. a prompt and a seed that makes ChatGPT print its input) essentially cannot be proven false by an author who hasn’t taken special precautions against being falsely accused, so the bar for sanctioning people based on its output must be much higher (infinitely so as far as I am concerned).