The reason they donāt want navigation at the bottom of the screen is because there are navigation buttons on the system (Home, Menu, Search and App Drawer).
On many phones, these are soft buttons (without physical separation between the buttons and the screen). Therefore, if you ask the user to click in this area, it is easy to "push with a finger" and launch from the application (by accidentally clicking the "Home" button).
Of course, itās important to follow design standards to make the app āfitā in the Android ecosystem, like other posters.
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