That's fine, you can do that if you want...
I just find it very convienient to be able to "divert" the flow from either fuge or skimmer chamber (thru "H") when shutting down a "portion" of the S/F for cleaning or mainenance...
Awhile back I had a "snot like" break out in my fuge...had to shut it down, clean it out, reset the sand bed etc...took a couple days...I was able to divert all flow to skimmer side and keep main pump running...Same as when I pull my skimmer and suck the junk out of overflow/skimmer/settling chambers...divert all flow thru fuge and keep return running with out sending all the skuzz up to the tank...