"so unless your pulley and line is easily movable, "find the string fulcrum and draw a line" could be better stated as "adjust the seating of the bow handle such that the string fulcrum is directly above the line and pully"
Yes, that would work just as well.
I have a lower pulley set up like Roy's, except mine has four pullies on it, so I can draw the bow as a split finger shooter or 3 under shooter, whether the top limb is facing right or left, all without moving a pulley. Being able to flip the bow around helps to verify that you have your tree setup properly as well as verify what the bow is doing, what you're seeing, and deal with some natural selfbow stave irregularities. With multiple pullies, I can change string position in 2 seconds.