Jenia, I think that the rooting all over the cutting is because they were cuttings with very little 1st year wood, and were mostly 2,3,4-year wood because they came from a mature tree that grew very little each year.
I have also noticed that several had tons and tons of roots, but seemed to have more difficulty producing a shoot - especially if there was no 1-year wood at the tip - perhaps because the buds were older and less "motivated".
I have heard in the past that the best rooting cuttings has a little 2-year wood at the bottom end, and this experience seems to have added credibility to that idea.