This. I would be filming to prove that I wasn’t luring the kid into the stall.
The little guy has a endearing trust in his neighbours. 
“Hey, there’s a guy in here, I bet he can help me wash my hands.”
Reminds me of my 3 year old, who loves nothing more than to barge in on me, lean on my knee, and tell me a long and complicated story about Spiderman, all while I’m poopin’.
I don’t think it was staged. I traveled alone with my daughters when my youngest was 3 and the oldest 7. There are many complications to that but one was that I had to send them into many bathrooms alone including busy airport bathrooms and just hoped they would come back out at some point without causing much damage to themselves or others. Single fathers can’t just march into women’s bathrooms to help if things go wrong and the same is true for mothers and young sons. I don’t know if they ever did anything like that but I wouldn’t put it past them and there wasn’t much I could do to stop it. Opposite sex parenting is fun but it has its complications.
I found an example… this particular vlogger is particularly bad.