Your video shows it's user error on your behalf: you chose not to send the email invite by pressing the Do Not Send button, but the user is still invited as you have specifically added them to the appointment by their email address. If you had used the Continue Editing button, or the close X at the top right you would see they are guests added to the event. The big pop-up asking you if you want to send an invite is telling you they are added - I'm not sure how you would interpret that any other way.