I think we talked about this before, but this was the rule (at least orally) at Calgary 70.3 this year. There were 8 penalties handed out (times are denoted on the
results) and at least 1 of those was a dismount line penalty (my wife witnessed they guy basically ride into T2 and the official run over and tag the guy). There were 869 finishers. There were 100 WC slots on, so there were a lot of guys out there who wanted them with the race in Canada this year.
Some might say that this shows the race was clean, but my n=1 is I saw lots of breaches. Not so many "trains" but at least half a dozen instances where I watched 2 or 3 guys hang out in the draft zone for 30 seconds plus. In at least 3 of those instances I watched the marshall either ignore it or give a warning. Basically, lots of people were willing to take a chance that they were not going to be the 1 in 100 who got popped for drafting.
Like any sport, there's the "rules" and there's the way the game is played.This is the way it is played. I don't begrudge those who want to change it but I suspect the vast silent majority are just happy to take their race results or qualifiers, shrug their shoulders and pay the next set of race fees.