Now that doesn't mean it couldn't be a reference like "'Jacob Neusner is know-nothing' and all that you wrote about at Stephan's blog ..." but it isn't usually used in this way. The exact phrase appears only in letters from Crocodilopolis (at least that I can find) and these letters are said to be some of the earliest witnesses of a Christian presence in Egypt. I also see no evidence yet that Morton Smith ever looked at these documents which were stored in a museum in Berlin.
An example from the so-called Letter from Apollonios to Zenon:
Ἀπολλώνιος Ζήνωνι χαίρειν, ὀρθῶς ἐποίησας συλλαβὼν τὸν ἐκ τοῦ ζυτοπωλίου ταμίαν. ἀπεστάλκαμεν δ̣ὲ πρὸς σὲ καὶ Ἀμε[ν]ν̣έ̣α̣ [τὸν] ζυτοποιὸν ὅπω̣ς̣ περὶ ὧν ἔγραψας κατ̣η̣γορεῖν 5αὐτοῦ τὸν ταμίαν ἐξελέγξηι ἐπὶ Πέτωνος τοῦ χρηματιστοῦ [P.Cair. Zen. 2 59202]
We are told in the letter that Zenon has done right to arrest the treasurer attached to the beer-house. Apollonios has sent Amenneus the brewer to Philadelphia in order that the treasurer may be confronted with him and convict him of the charges which he has brought against him. The case is to be tried before Peton the chrematistes, who is coming specially for this and for another affair (see PCZ.59203 and 04). If Amenneus appears to have really spoken as reported, Apollonios threatens that he will have him hanged.
I am not a papyrologist of course and this is a very preliminary investigation but it would appear at least that it would be incorrect for us to just assume that καὶ τἆλλα περὶ ὧν ἔγραψας is a typical Greek formation. It seems to be very distinctive - appearing in only letters from Crocodilopolis as far as I can see (cf. BGU 2 471). Did Morton Smith ever see these letters? He could have theoretically but a quick search reveals nothing that I can see.
Again, I see no evidence at all that when Theodore was referencing γυμνὸς γυμνῷ that he was necessarily referencing a particular term he thought was in the mystic gospel of Alexandria. He was just asking about a well known Platonic concept alluded to in the writings of another contemporary, Maximus of Tyre.