I am an atheist, with that said.....
Maybe they just read the bible....... most JW's don't. It clearly says everyone should keep doing it and all partakers were not anointed in that upper room according to JW teaching. I am suprised it does not get asked more.
This being said, any interaction with a deity such as an anointing is by all standards a 'miracle' event. I hope for those kids sake, they are mentally strong, because unless they can one day admit their mistake, like many ex JW anointed, they will spend their life trying to explain why told people they experienced a miracle by god.