I believe she meant that when he's 13 she won't be making him accompany her to the women's bathroom.
If I read the poster's previous posts correctly, her son was molested at age 4, in a bathroom, while a relative was present but apparently not paying attention. He was able to tell people at the time because he didn't know to be ashamed.
He's now seven. And he's still got severe lasting trauma to the point where he cannot go into a men's bathroom without shaking in fear. She doesn't expect he'll be any better by nine, either.
I'm really not sure how just turning 13 will enable him to "protect himself" any more or less than he can at 9. Most 13 year olds can't kick a grown man's butt. But hopefully the therapy he's undergoing at the moment will have helped him enough by then, and he'll realize that strangers will come to his aid if he's ever in need.
That's why I suggested using the companion restroom in the interim.
Her situation is not typical or usual, and I'm not sure it really applies to this thread. MOST nine year old boys would be perfectly capable of handling themselves in a WDW washroom. They're old enough to know that if someone makes them uncomfortable in any way, they can leave and tell their mother, who is waiting outside. The odds of any harm coming to a 9 year old in a WDW bathroom is much, much less than the odds of that same family having a car accident on the drive to Disney.
There's never to my knowledge been a recorded incident of molestation in a Disney bathroom. There WAS one story about a peeper... in the women's bathroom!