Snipped and bolded by me!
I think you are correct, the alleged 'intertwining' of alleged bone fragments with the wires from the steel belted tires has more to do with how the fragments were handled and says nothing one way or the other about whether the body was burned in the fire pit.
A few moments reflection will reveal to anyone the truth of this - pour ashes containing chunks over a mesh of wires and some chunks will become entangled in the wires. A colander that you use for straining pasta works on the same principle. This isn't rocket surgery!
Based on Sturdivant's testimony, it would appear the cremains were found in a discrete pile within the area of the fire pit. Pretty obvious that these bones were placed there after a fire, and not a part of any fire taking place in the pit.
I'm rather too lazy to go through the mental gymnastics necessary to deny the bones were planted.
All MOO, naturally enough.