You can argue nature vs. nurture all you want, but the fact remains that in some universe they were capable of doing whatever it is you're judging them for doing, and based on what people have said, people "become" more like their dream selves--having abilities, or powers, whatever. So it follows that other aspects of that person would also transfer over.
I mostly just take precautions. I have several "If X person does Y" plans in place. It's just smart. Even if nothing happens.