Yup. I'm an Android user by habit, but were I to release a game for a mobile device, most of my effort would be around making sure the iOS version was as pin-perfect as I could make it.
Why do you rob a bank? 'Cause that's where the money is.
I'm fairly confident (without having any data/just guessing) that Pokemon Go generated more money on Android than iOS because there's more devices and I don't think iOS users are that more likely to ingame buy for this particular game.
Also if you use a free+add based model I'd once again say Android would do well.
For a one time buy game that's relatively expensive like MarioRun I agree with your statement though. And I'm sure the exclusive partnership with Apple has other benefits, being announced at the KeyNote is great free marketing for example.
