This is correct. They are allowed to charge whatever they want via iOS subscription, so that they could cover the 30% "Appple Tax" if they wanted to. They just can't tell people that they could get Spotify cheaper direct, which is the source of this antitrust action.
Spotify may apply for permission to have one link that does "not include, or be used with, language that includes the price of items available on the website". The OS will throw up an intermediary scare sheet warning the users of the dangers of the linkhttps://developer.apple.com/support/reader-apps/
What's not allowed is telling the users that it's available for cheaper in other places. But you can charge as much as you want.