1) The three most recent intermediate grammars make no reference to the clitic/non-clitic difference between ἐμοῦ and μου. In fact, of the three, only Porter even mentions the word “enclitic” at all—and never with reference to these pronominal forms
2) Wallace’s grammar has a consistent preference to synchronic description (or at least categorization). It is only in the chapter on pronouns that he feels the need to explain NT Greek pronouns with reference to Classical Greek. And even then, he merely presents the facts already present in the standard reference grammars. Specifically, how is the fact that Hellenistic Greek uses pronouns more than Classical Greek going to help the 2nd year student who knows nothing of Classical Greek? It’s useless information—it was useless information was it was said in Wallace & BDF, too.
Is this alternation between ἐμοῦ and μου so nebulous that the grammars prefer to avoid discussing it?
 Daniel B. Wallace, Greek Grammar Beyond the Basics: An Exegetical Syntax of the New Testament (Grand Rapids, Mich.: Zondervan, 1999); Richard A. Young, Intermediate New Testament Greek: A Linguistic and Exegetical Approach (Nashville, Tenn.: Broadman & Homan, 1994); Stanley Porter Idioms of the Greek New Testament (2nd ed.; Sheffield, England: Sheffield Academic, 1999), 135, 208, 215, 216, 217, 288, 310.
 BDF §278, Robertson, A Grammar of the Greek New Testament in the Light of Historical Research, 677.