Here is a youtube video. This person has Necrozoospermia which is the medical term for sperm that does not move at all. The sperm may be alive and just not moving, or the sperm may be dead. The black sperm is dead sperm. The clear sperm are still alive. With lime your clear non-moving sperm will wake up in the vj. With Necrozzoospermia those sperm will never swim.
Also please remember that x and y sperm are the same. If you could see for sure what they look like we would not need micorosort.
However, if you go in gold you can read the studies about msu. The thoery of msu is the high pH attracts y sperm. Can you look at the high pH and say all those fast moviing sperm are y sperm? no. But you can look at the fast moving sperm and know that the sort was good. On average those fast moving sperm will have more y sperm than x. Just like the slow moving sperm should have more x sperm than y.
So the main reason we look after a sort is to see if the sort was good. if it was good as discribed in the study in gold then we know the odds are good we have the sperm we are looking for
Also y and x sperm swim differently in flow. x sperm swim in zig zags and y sperm in strait lines. We are sorting by how they swim not how fast they swim