I'm ignorant here. Why does it matter to you if your code is running on ARM or x86?
Get a single core ARM instance for almost the price of a double core x86 instance. Not a great marketing speech.
For one thing, everyone is painfully aware of Intel's monopoly pricing a few years ago before AMD came back to life. To prevent this, 3 supplier of CPUs seems minimal, so there can be dynamism of check and balance. (2 is insufficient, as seen from Intel vs. AMD)
Google doesn't own a company that designs ARM processors (IIRC)