well I'm a bit unsure of this evidence. I think peter Sutherst put real doubt on this and further photographic evidence may well prove it.
It's true the original crime scene photos of the kitchen do not show the scratch marks. But that is due to how the photos came out making it impossible to determine one way or the other. The photographer was not looking for scratch marks.
The other argument was there was apparently nothing on the floor underneath the scratch marks. The photographer luckily taking pictures of that specific floor area.
The scratch marks were so weak any tiny amount of debris just went into the silencer & nothing would fall onto the floor.