A woody stem when cut from the plant will take longer. On the plant it would root the same as the "scarification" will induce the rooting as the hormones in the plant are available where as if it was cut off the plant these rooting hormones would not be available in as high of concentrations...
Im a little unsure exactly what happens....
When you wound the plant with scarification..... the plant heals itself with callus tissue......
callus is undifferentiated.....meaning depending on environment it can become either vegetative or root cells.....
this callus forms heavily at the sites of wounding.....
My inerpretation is.... that plant callus tissue...is sort of like stem cells.....