This is both correct and incorrect. This is correct if you refer to how early versions of the Mac OS X installer was packaged. The Classic environment framewor

This is both correct and incorrect. This is correct if you refer to how early versions of the Mac OS X installer was packaged. The Classic environment framework was always installed but a copy of Mac OS 9 was also required to be installed on the system volume as well—and this wasn't included when installing a fresh copy of Mac OS X from a CD. There was a limited period of time when Apple shipped and installed both Mac OS 9 and Mac OS X on Macs—so for those people, the Classic environment was "effectively" installed by default. Though to reproduce this you'd need to run the Mac OS X and Mac OS 9 installers from their respective CDs.