Hey Stan's the Man - Your right. The higher quality Heater Control Valves do designate which way the water should properly flow to help avoid any seepage when closed but the Chinese brand of knoc-ka-noff parts usually don't have "Fahrvergnügen" written anywhere on them.
A friend had tried several of the lower grade Chinese Heater Control Valves off Ebay for his daughter's car that constantly seeped hot water passed the internal valve in the "OFF Position" no matter the direction they were installed.
After a lap or two laying on top of his motor while swapping out a couple of duds, I had later decided to add the manual Generic Heater Control Valve on Miss Purdy just as a back up.
Michael