Update:

The pattern seems to work for catching mainstream Mac browsers.

Turns out the code WAS to send Mac Users to a different Flash Movie, (as several Monks correctly suspected) that worked around APPARANT bugs in Mac Flash Player. Not bugs that would crash the Mac Player, but make older Macs run in a jerky, non eye appealing manner.
Therefore, there was a seperate Flash movie for the Apple player, so that both Mac and non Mac Users see the same movie.

Nobody was denied content, or sent to any site asking them to upgrade/change browsers, unless they needed to install Flash player. Older Mac users were given access to a Flash Movie that allowed them to see same quality content as others.