I believe dogs most certainly suffer from separation anxiety. My brother has two small dogs. One is a Morkie (Maltese & Yorkie) and the other is a Maltipoo (Maltese and a Poodle). Both of these dogs absolutely adore him.
The minute he leaves the house they go to the door and cry for him to return. They don't know if he is just going to the car or off to classes for the afternoon, but every time is the same. Even if there are other people in the house, they wimper for at least 15 minute before going somewhere and going to nap.
The second my brother arrives the dogs go absolutely nuts. Jumping all over like they haven't seen them in years even if it has only been a few minutes.
When my brother sleeps the dogs are nestled up against him and he doesn't mind at all. If he gets up during the middle of the night the dogs are right by his side. If he happens to close them outside of the room, they will cry and scratch for him to open the door. If after a few minutes, my brother has not opened the door, they will go to other occupied rooms and scratch and cry at the door for them to open it. If no one answers the dogs go back to his and lay down right next to the door.
Dogs absolutely adore their owners!
Here is a picture of Bruce, the Maltipoo (via my sister's Instagram)
Wow! What an experience and thanks for the photo!
You're most certainly welcome! His mannerisms remind me a lot of the video you posted when someone is at the our back sliding glass door!