This might be fixed already - I can activate "Save for later" using accessibility inspector.

Is there anything else missing here?

I think I found some of the issues:

Now it's one accessibility element, that's properly labeled as a button. Should the label say what the button does - e.g. if the value is "saved for later" the label should be "unsave" since that's what activating the button will do?

I updated the label and value. When the article has been saved already - the action is "Unsave" and the value is "Saved". when the article isn't saved, the value is "Not saved" and the action is "Save".