Well fortunately my surname is not Newton, so magical assumptions are not part of my cranial furniture.
I arrived at my conclusion using the same method as yourself. As per usual in this debate you neglect the either/or perspective.
That is the fibers can arrive both as secondary and primary transfer. Your preference for a particular route simply underlines your cognitive bias. Which for the more knowlegable sleuthers will bring your promotion of a particular theory into question.
Your assertions regarding the fibers, regardless of color, are without foundation.
Really, why? Elementary school reasoning suggests there was more than one potential route of transfer, i.e. multiple.
As usual, you see bias where none exists. That the fibers could be there from either primary or secondary transfer is exactly what I've suggested, and exactly why I call the fiber evidence inconclusive. Or to put it in the words of the GBI - meaningless.
We cannot determine by which method the fibers arrived in their various locations. The best thing to do is not to pretend one transfer method is more likely than the other, and just solve the case sans fiber evidence.
The desire to pretend the location of the fibers places PR in the basement is where the bias comes in, but that's your theory, not mine. My theory of the case is not based on fiber evidence at all realizing, as I do, that the fiber evidence is meaningless.