here's the science behind topping.. when you cut off the main growth meristem, it redistributes the growth auxins to other parts of the plant, thus making the plant think that the new topped areas of the plant are now the main growth meristem, or atypical meristem if you will, and it will now concentrate the auxins, or growth hormones to the new tops, making them the new atypical meristems..
same thing holds true for lst and or supercropping.. once the atypical meristem is no longer higher than the rest of the plant, the plant forces the auxins into other branches, which makes for more main growth meristems, instead of the typical one that you usually get in untouched marijuana plants..