I know an app can be design with any approach, I just happen to disagree with theirs. However there's also a perfectly plausible possibility that that Google's

I know an app can be design with any approach, I just happen to disagree with theirs. However there's also a perfectly plausible possibility that that Google's use of material design in iOS is less about well-researched decisions and more about trying to get people used to the Android aesthetic so that they switch. I don't know if this is what's actually happening, but I don't think it's entirely outlandish, and it's what it feels like as a user of their products.