Knowledge Base subscriptions not sending article subscription emails

When someone subscribes to a knowledge base it shows on each article that it is subscribed in that knowledge article. It sends notifications for new and revised articles as per settings for knowledge base notifications. However it does not send article level notifications such as checkout and comment. When looking at the article subscriptions, I do not see the individual articles from that knowledge base there even though they show subscribed on the article (I assume this is why it is not sending notifications.) If someone is subscribed to a knowledge base and each article in it I would assume it would also send an email based of the article subscription setting. I cannot find any documentation from ServiceNow other then how to set the subscriptions.

Is this expected behavior?