That’s funny if true, because I’ve heard that other parts of the company dogfood to an extreme extent.
As a sidenote, I’m rather surprised that there’s no open source Cocoa IDE aimed at Apple platform development. TextMate 2 would make for a great starting point, covering the source editor and file tree portions. LLVM provides all of Xcode’s syntax coloring, error checking, etc, so that’s taken care of too. The three big pieces that’d need to be written are XIB/Storyboard editing, project editing (clang flags, code signing, etc), and integration with clang, iOS simulator, etc. It’s a big project for sure, but far from insurmountable. If it’s written with Obj-C/C++ and Cocoa/Foundation, many of its biggest users would also be its best contributors and the project could go far quickly.