I don't believe it. Why would the mother stand guard outside of a women's washroom while sending her little boy in? It would make sense if she was standing outside of the men's, but it was the Ladies. She could just go on in and wait outside the stall for her kid no problem. If only because other female humans might ask the boy if he was lost. Or the risk of embarrassment because little girls would point and be like; "OMG ur in the wrong toilet!!" and embarrass him.
Not like, "My mummy told me it would be very validating for my gender identity if I used this women's toilet at the grocery store!".
I'm just an uncle, but I've been to a busy amusement park with the nephew anklebiters and while I take them to pee, the mothers go into the women's facilities with the kids whether they be male or female. The kiddies are usually supervised, because as adults we cannot comprehend the level of idiocy a 6 year old can get up to in the toilet until they are stood there, toilet paper in their hair, pants stuck in their shoes, telling you they sat in something brown, but they try to run by you anyways to get back to the jungle gym. They don't sit there in a stall, while a 6ft, barrel-chested orc peers in at them and discuss their inner feminine feelings.