I think a real key to that move is the arm action. And the shoulders.
The knee doesn't cross the plane of the rubber which is necessary. You step to the 45 line. All very well done.
But, deception is further than that. It's in the arm and shoulders. In fact, I'm guessing you can't do this and throw hard to first base. Everything is committed to forward down the 45 line. Your weight is moving forward down the 45 line.
So you go further by actually committing the body to throw down the 45 line..........but you don't. So, not much left on the throw to first. But, you don't need it because the deception is so strong.
Curious. You have to trust umpires. And, my experience is most won't call this a balk even if it is. However, how often are you called for a balk even though you don't? Do you show the move to the umpire before you use it? Pre-inning...pregame? To get his ok? The reason I ask is that in a two man umpiring crew, they have absolutely no angle to make this call. And, most won't make the call if "they don't see it". So, another question. Do you use that fact to your advantage and ever balk intentionally, taking a chance to nail a threatening runner.