That being said, the rules book has always stated, "Taking an injury time-out for a non-injury situation is unethical." However, it doesn't prescribe a penalty for that. Common thinking among officials is that we would issue an Unsportsmanlike Conduct penalty if we judged that this type of unethical behavior had occurred. But, in a practical sense, there is little we can do to make that determination absent some very blatant actions or words by the "injured" contestant or coach.
It's a tough situation, and the injury time-out can be abused so that a kid can catch a breather, or get a quick coaching clinic on something the opponent has been doing successfully, etc.