In the video, the trigger is pressed down a tad before a final push releases it from the console. As the Joy-Con moves away, you can also see a small cylinder receding back into the top part of the inside of the controller; to me, that indicates that when you push the trigger, you’re actually pushing out that cylinder to help bump the Joy-Con out.
Here’s a GIF of the relevant part of the video:
GIF by Andrew Liszewski / The Verge
The mechanism to remove the Joy-Con controllers looks similar to what was included in a 3D-printed mockup that accessories-maker Genki brought to CES.
