it's not summon - it's a perpendicular autopark. different things
I think if you look closely starting around 7:33 when the video cuts away from him getting out of the car to the car moving on its own...
first you'll notice the driver's window was closed when he got of the car but it's open when it cuts to the moving shot. then a couple seconds later you can also see that the seatbelt is still buckled (shoulder belt across the empty seat)
so here's my wild guess theory how he did this
(no idea if this will work & not interested in trying this in my car! and kids! don't try this at home!)
1. put some kind of weight on the drivers seat (sand bag, etc), buckle the seat belt, THEN sit in the drivers seat. open driver's window
2. drive / line up for perpendicular auto park
3. press Start on 17" screen to start the auto park
4. tap the brake to Pause the auto park
***5. get out of the car
6. reach in through the open window, tap "Resume" on the 17" screen
7. start recording video once the car starts rolling; edit and post on youtube
*** I have no idea if autopark will resume after you open the driver's door. If so, perhaps this is a "bug" ?
If autopark won't resume after opening the door, well, then toss out my theory... maybe instead just a trained monkey jumps out of the window after initiating autopark?
BTW, the guy in the video is a buddy of Bjørn (of youtube & Tesla videos fame) named Jørgen - he appears in lots of Bjorn's videos. I bet Bjorn knows the trick used to do this!