Mike, there may be some other factors that apply concerning the "Instant Platinum Status":

1.According to the AAdvantage Member Guide
you can't be AA Platinum just by flying
other OneWorld carriers. "Members must fly
at least four segments on American
Airlines or American Eagle to qualify for
AAdvantage Platinum status within the
qualifying year." Maybe other FT members
can clarify whether this rule is
waived for the Platinum Challenge, but
I doubt it.
2.Normally they won't let you take the
Platinum Challenge unless you are already
Gold. A few people have reported that
they did it, but as a general rule, it's
not allowed.
3.If you qualify for the Platinum Challenge
before June 30, it's only good through the
following February (in this case Feb 2002,
not 2003).
4.When flying Economy Class on Cathay, you
can only earn AA miles on B, H, and Y fares
(the most expensive ones).
5.The Cathay All Asia Pass rules state that
you can't earn miles.