I don't know anything about GB programming other than watching the video, but my understanding is that it's not doing memory reads but rather transistor logic t

I don't know anything about GB programming other than watching the video, but my understanding is that it's not doing memory reads but rather transistor logic to determine which sprites have priority on that line. This is also why you have that 10 sprite limit, as the 10 active sprites end up getting pushed into hardware comparitors for that line. Explanation starts around 46 minutes into the video.