Comment approved by my wife, who is a Plato scholar. Your point that whether True Philosophers even exist is left open is the kind of problem she points out all the time in dogmatic interpretations. It sounds basic, but it's so important to keep in mind that just because a character says something (even if that character is Socrates), that doesn't mean it's the "view" of the dialogue. And you have to be careful to pin down exactly what is being claimed, as you point out with the conditional. Plato is a master (surely one of the greatest of all time) of creating a dynamic space to think in without settling the questions raised.
Saying Plato is "just asking questions" seems like a cop-out, he's responsible for what he implies, whatever character he makes say it. How about the allegory of the cave? The roots of fallibilism could be traced to that allegory - except for the part about philosophers, who are the ones who have escaped the cave and have seen the sun, implying that they gain access to the absolute truth.
Is every author who wishes to convey certain messages to their audience through narrative also responsible for every single thing his characters say? Character-driven narrative would seem to be at odds with such a view.
I was wondering about that too. But what I mean by "responsibility" is that the ideas presented have a definite form and don't get to evade criticism by being mercurial and shape-shifting. Not sure about art, like fiction. I'm not seeking to prevent authors from being ambiguously provocative, but it's a crappy way to reason.