Also other ingredients may be added to modify the medium with time. In my experience with African violets, virtually every explant formed shoots regardless if its orientation to the medium. Leaf surface up or down made no difference. I had lots of failures with explants on agar. Uprooting the shoots for transplant is also no problem.
Sand comes completely off the little roots with no carry-over.
The only disadvantage I found so far is that you can not see roots developing in the sand.