This ban includes watching videos. The law says they must take action to prevent underage persons from accessing their services. This means they will likely have to require login and age verify any accounts. The carve out in the article is talking about teachers and parents being allowed to show the content to the kids.

"The govt doesn't need to enforce the age check themselves or even provide or suggest a mechanism."

I suppose it will be up to the courts to decide what is reasonable as an age check. However, the government has said that they don't want to include full ID checks, which is why one would assume they would provide guidance on how to comply.