While it may have never been explicitly spoken, one of Microsoft’s core strategies with Windows Mobile was that it was an extension of the Windows desktop. Microsoft never considered developing a version ActiveSync for Macs because that would diminish the the tie between Windows and Windows Mobile. What I think is very clear evidence that Microsoft is treating Windows Phone differently is that they intend to release a Mac sync tool for Windows Phone.
Slashgear has an article about the Windows Phone 7 Connector For Mac along with screenshots. Ironically, the connector appears to be more like ActiveSync than the Zune desktop software that Windows users will use to synchronize with Windows Phones. The Connector will synchronize music and videos between iTunes and the phone and photos with iPhotos. According to Slashgear the Connector will be available for download on October 24.