I would suggest you contact Hal Hilton (who was behind most of the rules relating to towers, I think), Mike Blaszczak (who has to enforce the rules), Bruce Boyd (who's the race chair), or Wes Tipton (who is, I think, the race co-chair).
FWIW, I don't understand the rule, either, as I don't think I've ever seen anything less than a 2 1/4" dry-break at one of our enduros. I know mine is 2 1/4".