A good example might be to look at sleep consultants and books about sleep training infants and small children. What they will tell you is that a baby can learn to go to sleep for bedtime independently, and they can learn to take naps independently, but learning one doesn't mean they learn the other. You have to do it for both naps and bedtime. Babies "know" when a nap is a nap, and when nighttime sleep is nighttime sleep. That is to say, humans are diurnal.

Also keep in mind the context of the article. We're talking about insomnia. You're invoking the idea of behavioral habits ("teaches your body)". In fact, the recommendation for not napping comes from behaviorists, Cognitive Behavioral Therapy for Insomnia. I imagine that the idea is to do things that maximize the chance that you actually get the behavior you're aiming for and building on that (maximizing sleep pressure felt during bedtime).

I don't think there's anything wrong with napping for someone who doesn't suffer from insomnia.