You gotta realize that Taylor's test rods are clean, new polished.
When they start to pick up and retain abrasives, you will have different results.
In the mold polishing and honing businesses, the brass lap is a fantastic tool. Why brass? Because it's soft enough for abrasives to embed itself into the brass.
Wood will also pick up abrasive, as Rich said.
Fibreglass is abrasive all by itself. I would never, ever, ever, ever, EVER use F-glass in a rifle.
Steel is hard enough not to pick up much abrasive in normal use. For shooting at the range, I use a polished steel rod, with a cone muzzle protector. The rod seldom touches the bore.
Taylor, you bring up a sore point about all the water squishing out around the cone. I've had same experience. How about making a cone with a drain on the side? C'mon, all you brains. We have an invention hatching right here! When you go to sleep tonight, you will dream of women, I mean, of perforated patented anti squish muzzle cones.
Give us the full report in the morning.
Or, maybe not.
Acer.