We are straying from the original topic a bit, but I think we have answered the question.
The only reason I can think of for not using a santee on it's back for a vent connection is if a cable machine is sent down the vent, it might turn back toward the fixture instead of going downstream.
The only reason I can think of for not using a santee on it's back for a vent connection is if a cable machine is sent down the vent, it might turn back toward the fixture instead of going downstream.