On iOS, the Tab focus and blur events fire for the relevant tabs when a tab is selected. On Android, these events also fire when the window gains or loses focus, such as when the Home button is clicked or when the screen is unlocked. The iOS behavior is the correct one, and should be matched. This is important, since we need a reliable indicator for when a tab is selected and unselected. We currently have no such indicator in Android, thus this is critical.
UPDATE: see PR in comment below. The PR added the selected and unselected tab events for Android, while not modifying focus and blur behavior to maintain app compatibility. In iOS, tab focus and blur were simply renamed to selected and unselected. These events function as expected, and have the benefit of being more appropriately named.