The Eggman Cometh, Did anyone else miss this joke?

So I was rewatching UA with a friend who has never seen the series before when he pointed out a "joke" I miss. Which I hope was a mistake on the writers parts. The joke was while Natalie was making cookies while listening to the recipe on the radio the lady on the radio told a story about how her nephew had a allergy attack after kissing a girl who just ate a peanut butter sandwich. Causing Natalie to throw away the peanuts, and late tell Gwen not to eat any peanut butter sandwich when Gwen said she was going to Kevin's house...The thing is Kevin was never established to have a peanut allergy...Ben was...So was this a mistake on the writer's part, which I hope is the case, or did one of the writers just made the joke I think they did?