What's the big deal about the pull up? I think they make it in sizes large enough for 5 year olds, so I don't think it's that weird. I have 5 kids and none required pull-ups by the age of 4 though, guess I was lucky.
I do wonder if she mentioned she put him in pull-ups so it sounded more likely that he was really in his room taking a nap? As opposed to him just twiddling his thumbs in there during her supposed nap. In fact, I wonder if he was routinely just stuck in his room so she didn't have to deal with him. I bet he was so scared and by the sounds of it his personality was that of a sweet compliant child.
Not that I think any of the nap crap story was really true anyway. I could also see her sentencing him to his room for long periods and not allowing him to use the restroom (for some reason on these boards I've heard horror stories of abuse where kids aren't allowed to use the restroom). By using a pull-up, it wouldn't be as messy to clean up and she'd have plenty of reason in her cruel mind to humiliate him for "accidents." I wish I didn't have to think this way. There's no telling all this poor little angel has had to go through.