Center Android WindowBackground with Activity ImageView

Use background instead of windowBackground

<style name="ColdstartSplashTheme" parent="SuperbalistTheme.Dark">
    <item name="android:background">@drawable/splash_background</item>
</style>

android:fitsSystemWindows="true"

That is your problem. Your FrameLayout start to inflate under statusbar, which height ~25dp, therefore AppCompatImageView a bit higher.

First solution: Remove android:fitsSystemWindows="true" from activity_start_onboarding.xml FrameLayout.

Second solution: Add <item name="android:windowDrawsSystemBarBackgrounds">true</item> to your ColdstartSplashTheme. The background starts drawing under status bar and bitmap will be higher.