But here's the thing, across operating systems the products should not be identical.

When you get to the point that your have a significant enough number of users across multiple platforms, generalizing everything into a shared UX doesn't make sense; giving those classes of users the best experience requires embracing their platform.

A simple example: Android has a system-wide convention for a `back` button. iOS has no such standard. Users on each platform have different expectations for how to navigate an app fundamentally, and holding tightly onto the concept of identical gives both camps a compromised experience.