Has anyone else noticed that sometimes when you go into Google Play on your Android phone and go into the "My Apps" section to see if there are any new updates available for your installed apps, that somestimes an app is listed as having an update available but when you tap on the app to see the details you only get "Open" and "Uninstall" buttons and no "Update" button?  If I flip back to the "My Apps" list and then back into the update then sometimes the "Open" button changes to an "Update" button, but not always.  

This is on my S3 with the stock 4.1.2 rom.