Go suit and tie. You have to remember that most of the judges are older more traditional directors. Some of them will get salty if you arent dressed properly and it will psychologically look at your group in a different light from the get go. Its kind of like doing a march on at marching contest, if you are out of step during your march on then you are already worse off out of the gate. It wont affect your overall scores directly but if you are on an edge it might get you less forgiveness.

Is it right? Of course not.
Does it still happen? Absolutely it does. Even if its not conscious by the judge.

Gotta play the game.