Thank you Andrew. Another of the reasons why I think the link between Ambrose and Tatian is possible (aside from the Syriac reference identifying 'Ambrose' as the author of Tatian's treatise) is that Ambrose and a 'Tatiana' are identified together in On Prayer:
Now, my most religious and industrious Ambrose and my most honest and manly Tatiana, from whom I vow womanish things have vanished just as they did from Sarah (cf. Gen. 18:11), you are probably puzzled as to why, when my proposed subject is prayer, I speak in my preface of things impossible for human beings made possible by the grace of God.
Ἀλλ' εἰκὸς, Ἀμβρόσιε θεοσεβέστατε καὶ φιλοπονώτατε καὶ Τατιανὴ κοσμιωτάτη καὶ ἀνδρειοτάτη (ἀφ' ἧς ἐκλελοιπέναι «τὰ γυ ναικεῖα» ὃν τρόπον ἐκλελοίπει τῇ Σάῤῥᾳ ἤδη εὔχομαι), ὑμᾶς ἀπο ρεῖν τί δή ποτε, περὶ εὐχῆς προκειμένου ἡμῖν τοῦ λόγου, ταῦτα ἐν προοιμίοις περὶ τῶν ἀδυνάτων ἀνθρώποις δυνατῶν χάριτι θεοῦ γινομένων εἴρηται
From the end of the same treatise:
And so, my brother Ambrose and my sister Tatiana, most zealous for learning and most genuine in your religion, these are the results, so far as I have been able, of my wrestlings with the subject of prayer and with the prayer in the Gospels of my wrestlings with the subject of prayer and with the prayer in the Gospels, together with the passage before it in Matthew.
Ταῦτα κατὰ δύναμιν ἐμὴν εἰς τὸ τῆς εὐχῆς πρόβλημα καὶ εἰς τὴν ἐν τοῖς εὐαγγελίοις εὐχὴν τά τε πρὸ αὐτῆς παρὰ τῷ Ματθαίῳ εἰρημένα ἡμῖν διήθληται, φιλομαθέστατοι καὶ γνησιώτατοι ἐν θεοσεβείᾳ ἀδελφοὶ, Ἀμβρόσιε καὶ Τατιανή.
One should note that the 'brother' and 'sister' reference is just the plural 'adelphoi' used in the Greek. Both Ambrose and Tatian are in the vocative. I guess Τατιανός is the assumed form of 'Tatian.' But who is this Tatiana? No one knows. The purported wife of Ambrose is Marcella. Could it be the text was altered to make Ambrose and Tatian appear as different people? The use of the plural 'gospels' and 'Matthew' already raise my suspicions given the pattern we have seen in other texts. It is noteworthy that when Origen addresses his patron in what is left of Commentary on John Book 5 no specific name is mentioned. Someone likely came along and made specific that 'Ambrose' was the name of Origen's patron.
It is worth noting that the 'manly' business being associated with the female 'Tatiana' is also associated with Ambrose in other treatises. Note the beginning of Commentary on John:
But what is the bearing of all this for us? So you will ask when you read these words, Ambrosius, you who are truly a man of God, a man in Christ, and who seekest to be not a man only, but a spiritual man.
Τί δὴ πάντα ταῦθ' ἡμῖν βούλεται; ἐρεῖς ἐν τυγχάνων τοῖς γράμμασιν, Ἀμβρόσιε, ἀληθῶς θεοῦ ἄνθρωπε, καὶ ἐν Χριστῷ ἄνθρωπε καὶ σπεύδων εἶναι πνευματικός, οὐκέτι ἄνθρωπος.
“Finally, from so little sleeping and so much reading, his brain dried up and he went completely out of his mind.”
― Miguel de Cervantes Saavedra, Don Quixote