It's not that they can't express their feelings, they're just not expressing them in negative ways. From the article:

We're training them to yell when they get upset and that yelling solves problems.

You know how they used to say that when you were angry to go hit a pillow to vent the aggression at something that wouldn't harm anyone/thing? And now they say that's bad because it just trains our brain to associate anger with acting out physically? It's the same thing. They express those feelings, even anger, without aggression. Being outwardly angry does nothing other than potentially escalate a situation. But train children early on to respond to anger in healthy ways and they can respond calmly and rationally for their entire life.

"When you try to control or change your emotions in the moment, that's a really hard thing to do," says Lisa Feldman Barrett, a psychologist at Northeastern University who studies how emotions work. But if you practice having a different response or a different emotion at times when you're not angry, you'll have a better chance of managing your anger in those hot-button moments, Feldman Barrett says. "That practice is essentially helping to rewire your brain to be able to make a different emotion [besides anger] much more easily," she says.

So there was a whole article that talked about using proven methods for developing healthy behaviors, but you read the short bit about them telling stories about monsters and used that to try to discredit the whole thing? AND you ignored the part where they talked about how those stories enable them to teach children about dangerous scenarios without actually putting them in danger? It's whole purpose for being there.