No theory fits all of us....
The problem starts when people start approaching our behavior scientifically, and want one theory and definition to fit all of us, so we can be categorized. Unfortunately it won't work; there are so many different combinations of reasons that there is no 'one size fits all', and no stretch of the imagination can ever twist the logic enough to make us all fit into one box. The folks who wrote up those web pages may have themselves 'pegged', but that doesn't mean it applies to everyone. I'm guessing that like everyone else in the world, they need to feel that there are lots of others similar to them, and so they just assume that is the case.