iOS seems like a huge counterexample (as you note.)
For Android development on the other, you don't have a good simulator, and the out-of-the-box dev experience relies on an x86 emulator of the ARM environment. In practice this means that in your day-to-day Android development, you're running the compile-run-test cycle by looking at your actual ARM device all the time, because the emulator is dogshit. I wouldn't really call it cross-platform development in any traditional sense, it's more like remote development, and a bad experience.
This hasn't been true for years. The emulator shipping with Adroid Studio uses an x86-based image, and it's very, very fast as a result.
Android's emulator even has quite a few more features than iOS's simulator, such as mock camera scenes so you can even develop apps that rely on the camera on the emulator.
If anything these days the Android emulator soundly trumps the iOS simulator on all interesting metrics except maybe RAM usage. But, critically to Linus' argument, they both use the same architecture as the development machine.
And the fact that the "develop on x86, test on ARM" workflow works so smoothly on iOS is strong evidence that Linus is wrong.
I’ve certainly heard of bugs that the simulator doesn’t reproduce because it’s not ARM.
And that isn't enough to get people to demand an ARM emulator. In fact, Android developers hate the ARM emulator and prefer the x86 simulator—more evidence against Linus' assertion.