iPhone vibrates for text messages when Sleep Focus is active

My focus is set to "Sleep," but my phone still vibrates every time I get a text message. Intelligent Breakthrough & Silencing is toggled off. I have not modified this focus to allow any notifications from people or applications to come through. Notifications options: Show On Lock Screen = Off, Silence Notifications = Always. I have music/ audio books playing, but my phone is locked. Why am I still being notified of text messages?