Liked the video
But, by the title, I thought you were going to teach that backhand topspin serve from Asuka Sakai.
.... Also, there isn't really any other serve you can do if you start off like that so the opponent will know you are gonna do a fast serve. Also, I'd like to see how often he succeeds in doing that, especially during a match under pressure. The pendulum serve is just a much more practical serve and is more deceptive because of the motion.
....I use it together with a pendulum serve, emphasizing on short diagonal. And then slam fast dead ball straight close to the edge to oponent FH. Also when serving, both of them look a loot the same until the final stage of serving. If the serve goes as planned, the opponent sometimes even fails to move