He’s not approaching the ball any differently than anyone else until a fraction of a second before he actually strikes the ball. Even if it was the approach like you’re saying, that has nothing to do with the backflip itself…you can do the same approach without the backflip, it changes nothing about the end result.
All that happened here is the goalie committed to go to his right and then froze when he realized it was going the other way…not to mention the shot placement was unsavable anyway. Played goalie for years growing up and even when you’re up against teenagers with a lot less power you have to start making up your mind long before you would ever notice anything off with this particular approach. You can’t wait until the moment they kick the ball to make up your mind, the ball literally goes from the spot to the back of the net in less than half a second, and it takes you just as long to move your body to wherever you want to block, you can’t wait until the ball has been struck to decide. I think you’re massively underestimating how much time it takes to process what’s happening in a situation like this.