Phil in Shakespeare "is the courtier supersmart or just not as gullible as the rest?" Whichever you like but what makes it interesting on the stage is that the blind guy is tricked in a way not even the audience perceive until it is explained by the courtier (see reply to Bitter Crank). I don't think Shakespeare's interest was philosophical, I think he made use of a philosophical party-trick (don't pay too much attention to the label) to make a dramatic point which is the smartness of the courtier. FYI, the purpose of showing his smartness relative to the rest is to increase the horror of him being brought low and killed by them.
Also FYI, when I came across this in the play it struck me as identical to something I'd come across in university philosophy but I couldn't recall what. That's why I ask if it seems familiar to anyone else. Maybe something from one of Socrates' cross-exams?
As for the philosophical issue, I agree that what it touches on – how colour-words name for example (obviously not simply by ostensive definition) – seems more modern (e.g. Wittgenstein). That's what makes it interesting. I don't think Shakespeare came up with it, I think someone more philosophical gave it to him and he just made use of it.