Judging anything "artistic" is totally subjective. It is impossible for any judge not to have biases or prejustices that influence their decisions. Right or wrong, it's just part of the game.
I have been away from the Bonsai world for 20 years, and haven't been showing, so I cannot give specific examples, but I can identify with the frustration you are experiencing.
Totally unrelated to Bonsai: My daughter got into showing horses. First local shows, then 4H, then big time 4H, then in the big AQHA (Quarter Horse) shows. As we moved up, the competition got tougher, and the importance of 1) knowing the Judges and what each looks for; 2) having the correct style and color of saddle; 3) having the right show clothing;, 4) having horses of a certain bloodline, etc., mattered.
Sometimes, you would have to show in front of a particular judge several times before they would "really look at you". If they had seen you ride in previous shows, then they knew you were serious, and would therefore look at you more, which meant you were more likely to get placed than a rookie.
Also, the big horses seemed to place higher. Don't know exactly why. It was first apparant to us when we bought our daughter's show horse. She had shown another horse successfully at local and 4H, but we realized if she were to really compete, she needed a better mount. And we found one, trained by a successful trainer who took horses to the World Quarter Horse show, and placed well there. And, when we walked in her barn, we noticed that the horses were all "big" and much taller than the horses most folks have. Or, should I say, much bigger and taller than the horses WE had, and bigger and taller than the horses we had been competing against at our local shows.
The horse we bought was past his prime, but still extremely talented. He took my daughter on a great ride: She was State Champion in 4H, placed 7th in the Southeast 4H championships, and she competed in large and small AQHA shows. She could do well in the small AQHA shows, but the big AQHA shows would attract the Million dollar horses, and well, when the horse was 6 he could compete against those guys, but not at 16.
But I digress... the point I'm trying to make is judging horse shows is 100% totally subjective, similiar to showing bonsai. Styles come and go. Sometimes conifers are preferred to deciduous. Sometimes you have to have to have an antique Chinese pot, or a hanging scroll, or the perfect accent plant, or whatever, to win.
If I may give one more example: Some Quarter Horse shows would have two judges. You could earn double points by showing at a "Combined" show. In one event my daughter won the Blue Ribbon, under one judge, and did not place under the other. Go figure.
JRob, I think your shohin are incredible, and I wish I had your talent for it. It is unusual that you started off directly into shohin, I think most start with larger trees, then migrate to the minimalist shohin after they have mastered the art. Congratulations to you for your ability to "skip a step"!