I think they mean just roll with the bike. IOW, don't try to do anything once you've started going over. You'll land more gracefully given the situation and lessen your chances of actually injuring something. Unless you're going at high speed, you're not likely to break a collarbone in that kind of situation, but if you put your hand down to break your fall, you can do nasty stuff even after coming to a stop or close to it.

I used this method the only time I've fallen and it worked for me. I had just gotten a new bike and got a new set of pedals with it since I was keeping my old ride. The tension on the new pedals was set a bit higher than the old ones and once after a really long ride when I was just too darn tired, I didn't use enough force to disengage. I lowered the pedal tension after that incident, but luckily nothing came of it.

If you use this method, you'll also drastically reduce the chance that you'll hurt your bike too because it will just come to rest on top of you.