How does filters on google play work?

I wanted to restrict my game to Android devices with larger screen sizes. So I used following tag in my manifest file.

<supports-screens
	android:smallScreens="false"
        android:normalScreens="false
        android:largeScreens="true"
        android:xlargeScreens="true"
	android:requiresSmallestWidthDp="600" 
/>

I assumed it will not work on small screen devices based on the settings.

When I “Build and Run” or copy the apk file to the device, regardless of the tag setting it works.

Am I using this tag incorrectly or it only works when you upload the game to Google Play?

Google Play uses the filter
restrictions described below to
determine whether to show your
application to a user who is browsing
or searching for applications from the
Google Play app

It seems like its for filtering, and not actually block anyone from trying. More to prevent customers to get something that is not supported for their device. And yes Google Play will read the file on upload.