At first I thought you were crazy. I have the full vid and have watched many times. Now with this clip, I compared to my vid and see the same as you. Those casings disappear when they contrast against the white exterior wall, and there is no sound of them plinking on the ground, which is concrete
There was someone getting in the car to his left when he first approached the area. They more than likely high tailed it outta there after he opened fire at the doorway
I too wish people understood the difference between the two when referencing a magazine as a clip. I have not seen anyone use clips in forever