If you're being judged on craftsmanship though, feedback is important and gives transparency to the whole process and allows people to AVOID having hurt feelings, as they understand the specifics of why they placed where they did. The vagueness hurts the judge-competitor relationship more than any criticism of the costume will.
Additionally, there's nothing subjective about craftsmanship of a costume. Either the quality is there and it's done right or it isn't. If two things are of the same craftsmanship, move on until one costume shows superiority.
I also disagree about what you said about sewing specialists being more impressed by armor. It actually highlights the need for a panel with very diverse skills. You wouldn't place a Nurse in charge of a Particle Physics committee because they're more impressed by it than a Physicist.
Overall, I feel the reason people are concerned is because the dominating feeling is that the judging is opaque/subjective, and that craftsmanship isn't being valued properly.
"The important thing is no one was hurt... No one who counts."