I don't know, but all sorts of things can happen, and I didn't want to exclude people who somehow just have one or the other. (This is the kind of matter about

I don't know, but all sorts of things can happen, and I didn't want to exclude people who somehow just have one or the other. (This is the kind of matter about which I expect not to be very knowledgeable, so I just moderate my language towards the "I don't know everything, might as well make it so I don't exclude people" end.)