It's not going to be that simple, because Xcode can't build Windows applications. Adobe will have partitioned out the project so that as much code as possible will compile nicely under two separate environments.
I agree... plus its not like you can even port portions of the code over to and from the two environments very easily, since you have to use VB.Net or C#/VC++.Net on the Windows side, and Obj-C on Mac. Granted, you can use C++ code in XCode, so theoretically if you wanted to segment some of your background processing routines/classes from your framework calls, you could have those classes be portable. But I've never attempted using C++ in an otherwise Obj-C program.
(sure you could use Java for cross-platform capabilities, but not really in this instance. Any hard-core processing must be done by a fully compiled language, or you're an idiot)