The struts just jump off the release with SKS. With Planet Bike, if you are fast enough, you take a flight and the fork is likely a goner. The situation appears here similar to that with Ford Pinto. Metal fenders do not need a release, because they lack the flexibility allowing them to grab the tire and fold inwards locking the wheel.
Oh, I was just wondering because my brand new SKS fender on my Bridgestone just jammed up my front wheel this week despite the releases. Luckily I was traveling slowly. This is a legit concern with any fender in my opinion. Keep spreading FUD around, though.