As I stated, I've been intimately familiar with the rules since I started doing this...indeed, I ran across this "new" rule while on the Ace Race site seeing if anything had changed, which is when the reworded verbiage caught my attention. It was never specified, or even implied, that TDs couldn't do what I and others have been doing for a while. I would expect an official "Rules Update" announcement from DC rather than having to discover these things on my own...
And I agree with others that this rule doesn't prevent anyone from getting familiar with the disc before the event...I've always allowed early check-ins to warm up and even get to know the shortened holes, and yes people will "speed break-in" the discs with some pavement or tree throws. I've never had a complaint in regards to fairness, because as far as I know people show up to have fun, and the more aces and metal hits ALL AROUND the greater the collective fun factor, so I still don't get it. :\