For the record, I have never done "AI hiding" because I don't think I can make good use of it with the risk associated with it. I may have even lost a first place to it before, and I think it's great. All this to say, and being fully aware this is a controversial opinion, I see absolutely no problem with people making use of it, and I am not even defending it because I am using it, far from it.
In fact, I have a hard time understanding that perspective. You can't force people to have their best version out. If through a lot of thinking and testing you discover an awesome strategy, why would you be forced to show it to everyone, why couldn't you keep it secret and reap the benefits of your creative thinking? Since it's a competition, such mind games are part of a healthy, competitive community. If you are playing within the rules of the game and the competition (and this is the important part), it is your responsibility as a player to use everything at your disposal when you play to win. I have a lot of respect for that.
I strongly recommend reading this classic and great article on the topic of playing to win when having a competitive mindset. It addresses common arguments such as "this is not fun/fair/etc." and the approach to take when you want to win. While it's mostly about game design, you can also apply it to a "meta-game" such as a CG competition.
One thing to clarify, while I don't see any problem with it, it is possible that "AI hiding" is something that needs to be addressed as a whole, if it is the general desire of the CG staff or community and if there is a good case for it. But, and it's very important, this would need to be answered at the level of game mechanics / tournament rules that are clearly defined for everyone to see, and not with unwritten rules or something subjective as "it's not fair".
I would also like to sincerely congratulate the players who performed very well on GitC, "hiding" or not, for playing to the very best of their abilities within the rules of the tournament. There's been some impressive displays of skill there.