The rule seems to restrict more than can be verified in reality. Since you don't submit the source code, there's no way to tell what language you used. As long as it doesn't do dynamic code generation, everything should work.
(of course if you don't mess with the binary after compilation, the language could be identified in many ways, but you can as well change the result to look like whatever you want)
Ex Reverse engineer (and current iPhone Developer)
Nope, you can tell. Especially if you have the tool itself on your desk when you try to develop a test (as Apple will surely be buyers of). If it doesn't look like Objective C, C++ or C in its call parameters, flow, etc, they'll "know" well enough to hold you up in their queue process until you "send screenshots of the source"
The boilerplate code technique (where C code is generated) can even be detected (although has more false positives).
The Adobe sourced Flash binaries are supposedly trivial to tell, and I'd expect MonoTouch etc to also have that issue.
(of course if you don't mess with the binary after compilation, the language could be identified in many ways, but you can as well change the result to look like whatever you want)