It could be, but plenty of people book Business eastbound and economy or premium economy westbound for TATL.

This makes sense if the main value proposition of Business is the ability to sleep in a flat position, which is much more valuable on an eastbound redeye. In fact I am doing this on an upcoming vacation, since I will be traveling with my wife-- it's much easier to chat in Y/Y+ than in the J "suites"-- and both of us try to stay awake on westbound day flights so we would spend most of the flight sitting upright anyway. Hence the hefty additional $$ to sit in Business on the return doesn't really make sense.