First, why are there different ball lock disconnects at all for gas-in and liquid out?
Of more practical considerations, say you want to purge a keg from the bottom up. You would want to connect a gas-in disconnect on what is ultimately the liquid-out side. I know the different disconnects don't lock (or at least not well?) onto the opposite designed post. So do you put the gas-in post on the what would be liquid-out side to purge, then swap the post for normal use? Or, do you put a liquid-out disconnect on your gas hose? Does it matter at all?