To me no passing means no passing. Rules are rule and we can't decide when it's ok to break them. Yes, you lose time to the field if you're stuck in a slow group, but that's the game. I don't know for sure if the no passing zone applies to pros, but if so then the pros should follow them too.
I played cat and mouse with someone the last 5 miles of a sprint this year. Knowing there was a no passing zone at the end, I powered up the last hill and put him pretty far back, then pulled into the no passing zone cones behind some slower riders. Wouldn't you know it - the guy comes flying by all of us in the middle of the road ignoring the no passing zone and finishes the bike ahead of me. I wasn't happy.
It's sort of like NASCAR - not everyone gets the same treatment out of the caution flag, but you have to learn to deal with it.
The no passing zone on the bike here in Kona is in two places. The first is near the start of the race when you descend Palani coming down the hill there is no overtaking. And then again at the end of the bike course there's a small hill in front of the King K Hotel before the dismount line where no passing is enforced. It applies to everyone.