The Latin and Greek of Titus Pomponius Atticus

Cornelius Nepos, On the Roman Historians, Atticus, 4.1:

Huc ex Asia Sulla decedens cum venisset, quamdiu ibi fuit, secum habuit Pomponium, captus adulescentis et humanitate et doctrina. Sic enim Graece loquebatur, ut Athenis natus videretur; tanta autem suavitas erat sermonis Latini, ut appareret in eo nativum quendam leporem esse, non ascitum. Item poemata pronuntiabat et Graece et Latine sic, ut supra nihil posset addi.

When Sulla arrived at Athens in his journey from Asia, he kept Pomponius in his company as long as he remained there, being charmed with the young man's politeness and knowledge; for he spoke Greek so well that he might have been thought to have been born at Athens; while there was such agreeableness in his Latin style, as to make it evident that the graces of it were natural, not acquired. He also recited verses, both in Greek and Latin, in so pleasing a manner that nothing could have been added to its attractions.
[J. Watson's Loeb edn.]

Is this evidence that Greek at Athens during Sulla's time there (late 80s BCE) or at the time of Cornelius' writing (d. 25 BCE) was perceptibly different to Greek elsewhere, for example in Asia Minor ?