scott B.O.B. or Back of Ball aiming is in a nutshell; aiming at a point on the back of the O.B. that is in line with the CB and OB contact point.
That shadow method I use and teach to some is a type of B.O.B. aiming method.
Its a similar idea to using the spot on the wall trick for banks.......instead of looking at the exact point of destination you look in line with it and choose your point on the wall.....
Theoretically B.O.B. aiming should more accurately get the shot in the correct line, than just normal contact to contact aim as extending the line with a proper stroke should bring the CB to the contact point needed....a better word would be more PRECISE.
There is more than one "style" of B.O.B. as well......its interchangable with some common aiming systems as the contact line aimed to the front or the back of the OB will give the same contact on the front of the OB.
Basically the longer you can make your aiming line then the "straighter" that line can actually be or be seen.