I don't care what you may have been told, but READ THE LABEL. The jugs of RV antifreeze have labels. If it says Propylene Glycol (and maybe water) it i safe to drink, but it still tastes terrible to me. That stuff got expensive, so many manufacturers switched other more toxic but not deadly glycols and alcohols sometimes denatured ethyl alcohol. The reason for denaturing ethyl alcohol (ethanol) is to make it too toxic to drink.
That said, if that is what your RV suggests and you choose to do it that way, buy only propylene glycol. If you want to use the cheep stuff, figure out how to break into the system so you don't have to fill the potable tank.
Matt