Google has updated its back end so that movies and TV shows purchased through the Google Play store will now stream through the Android YouTube app (and on the desktop) under the Purchases section. As the change happens on the Google side, no app update is required on the user's part to enable this feature on Android smartphone and tablets.
If you've purchased any video content from the Play store, they will appear in the Purchases section of YouTube in chronological order based on the date of purchase. Unfortunately, you cannot sort this list or re-arrange the order.
Additionally, if you are more familiar with the Play Movies & TV app, you can also watch your purchased video content there as well, but this definitely adds more flexibility for users.