the racket tilt is more to push a rising ball (early striking) down to flatten the path of the ball (since a rising ball tends to continue to rise after hitting the stringbed) not so much to create spin.
watch the same player hitting the ball on the drop and he will hit with the same spin but a vertical racket face. the other reason for the racket tilt is that the ball is below the racket center when it leaves the stringbed (not at the moment of initial strike as the tennisspeed guy claims!) because the stringbed brushes upwards. this causes the racket to tilt.
I think with his opinion that the racket tilt increases spin the tennisspeed guy is pretty much alone.