I appreciate the sciency way you presented this but wanted to share a different perspective . The reverse needle is my new best friend . I actually went back and reverse felted most of my older animals and think it added a lot to the effect I was going for .
You can see some of it on my blog.....
Perhaps one of the differences in our results was different type of fiber as I have much better result using very thick layers of alpaca and mohair over a very firmly felted wool animal . I also make really large animals and use a four needle tool to do much of the felting and reverse furring . I think perhaps the morino "furring" is less stable when reverse felting because it breaks more then the alpaca or mohair ?
The down side for me is that it does take a little longer then rooting hair in as there are three steps....create firm sculpture, firmly felt thick layer of mohair or alpaca into sculpture, reverse felt and brush . I never got the hang of felting fur sections in that were firm enough for brushing .
So, I can see that really small animals or only using one needle would make this a pretty useless tool but for me it's added a new dimension to my animals .