Why is the WKF against groin protectors with removable cups? Is it because the cup might break rather than protect the testicles if, for example the wearer is accidentally kicked hard in the groin and the sides of the cup are not in their proper place?

I saw some good products at Karate Depot. However, I bought a Procup - one of those with a separate cup. Would you recommend getting the one-piece adidas one to replace it?