Yeah, I've read that too. I also know where you've read it. I find it funny that nobody has posted that they have tried it and how it worked for them. :lol: To me it sounds like you would end up with one solid color and a stained base.
What I like to do when I color is put the piece upside down on a styro head and comb the color through back hair, then the sides and wait 10 -15 min. After that I comb the color through the top and front and wait 5 min. This way i end up with the darkest color undeneath and on the ends and a little lighter on the top and sides. Kinda like a real head of hair.
It may take some trial and error to find the right color to use and to get the timing right, but I have found that if I use 10 volume developer I can go darker multiple times without damage to the hair. Of course once I found the right color its been a (is it doddle or doodle?).