Guys, I previously thought the same as you. But Neil Griffiths told me it is possible, if the belt jumps teeth and keeps turning the cams, for valves and pistons to hit. As I said, I do not know how, or understand why. I am just going by what he told me he has *seen*. There was also a V8 on ALSC, I believe posted by Lew, that had this happen, and bent valves.
I know that when I had my belt off, I could spin the cams and crank freely and not hit. Don't ask me how it can happen, but if Neil says it can, I believe him. He knows a lot more about, and has a lot more experience with these engines, than I do.
That would be why I said "it can happen, I don't know why".