I think the dark grey material is masking the bloodstains. Either the color, or perhaps it's less absorbent than the light grey.There's blood on the back of his sweatshirt, sort of watered down looking (for lack of a better term) in several areas. But when they take close up shots of the puncture holes on the arm of his sweatshirt, there's no blood at all. Nothing.
Even areas of heavy staining, like the left upper back show no blood in the dark grey sections.
![1717442132335.png 1717442132335.png](https://www.websleuths.com/forums/data/attachments/480/480564-a00ed3ca508697a0f1cd7f97f71a0f99.jpg)