It's definitely an important question. What's allowable/acceptable needs to be defined and has to be reasonable.
Why is 180 degrees acceptable? Not being a skater myself, when I started looking into jump mechanics and specifically the topic of pre-rotation, I found
these posts quite helpful (posts by Components). In the end, various resources helped me reach the view that 180 degree turn on the ice during takeoff is standard for loop/salchow/toeloop (as BoP described) and is acceptable/normal for lutz/flip.
If we look at the top 20 ladies at 2016 Worlds, all of them took off forwards on their 3Lz/3F, with the lone exception of Alaine Chartrand (who is in the league of Carolina Kostner with her backwards "power takeoff"). Caro/Yuna/Liza/Alaine may be the gold standard but I'm not advocating applying a penalty to anything less than gold standard, but just drawing a reasonable line somewhere.