It’s the perfect opportunity to teach them the lack of value of FOMO, especially when it’s validation from people who would bully you that you seek. I don’t see why what you’re recommending is a healthy response.
Teaching another person, even an eager one, how to change their behaviour and mental patterns concerning validation and FOMO is a really hard task. It's not knowledge like math or something that you can just pass onto them. It can take months or even years even for pros (psychitrists etc.) to do that. Combine that with the fact that teenagers brains are wired differently (their need to fit it is greater than that of an adult) and their "natural resistance" to adults' teaching and it becomes almost impossible task.
Ever tried teaching anything to teenagers where their peers and society in general promote the opposite? Good luck with that...
Like a strict parent whose kids end up doing drugs and partying as soon as they can leave the house, or even the opposite, some "hippie" all-too-liberal parent whose kind grow up and seek strictness and discipline, and e.g. turn religious or join a cult, or find some abusive partner who gives that to them.