Forgot to also mention the fact that the primer comes down at an angle as the action is closed.

Yep. When closing the action on a break open, the EDGE of the primer can be contacted and if you are "slamming" the breech closed it can and will go off if the primer is set out for a hard crush. The edge of a primer tends to be a bit touchy while the face is a bit tougher. That's why you have less problems with them in a bolt action accidentally going off when a hard crush is set up.