Yeah, no, sorry, this was the worst answer possible to this situation. The masked assaillant goes after a house and he chooses the most protected room in there ? That's both the simplest and most complicated answer.
The little sister mentioned the brother shut in in elementary school, and after 20 years he's a grown man, while she is still a young girl, as proven by her elementary school backpack. And thus a ghost reliving the night of her death. It's both more elegant and far more logical.
I'm honestly leaning towards "the explanation pages are starting to be straight up bullshit now." Which would be a good meta twist, I'll admit.