Bullshit. You don't even need to be doing game development for the simulator to be useless.
Every experience I've had with the simulator has been that it's entirely useless for determining how the code will run on a real device. I mean, hell, you don't even have actual iOS running on the simulator, you're running a Mac OS X binary!
The simulator is effectively WINE for iOS: it reimplements the iOS APIs under Mac OS X, and the toolchain compiles an x86 binary instead of an ARM binary. No one should have to explain why that's entirely useless for trying to build an ARM app on iOS.
It isn't just game development. I had a bog-standard iOS app that was a very simple UI in front of a website. Try it in the simulator and it seems nice and snappy. Try in on a real device, and it's slow as molasses and nearly unusable.
Why? Because it turns out some code being run in the UI thread was excessively slow. So it had to be moved out to a new thread. (Which, arguably, it should have been anyway, but I'm not the guy who wrote the original code.) But on x86, it was fast enough that no one even noticed.
I remember optimizing said chunk of code so that it ran in around 0.2 seconds on the simulator - and took nearly a minute on an actual device.
The simulator is entirely useless for developing an actual app.