Why are there no share fields in the Share buttons box?

The box offers Share title, Share summary and Share picture only while this plugin writes the Open Graph tags. Instead it says one of these:

• "Yoast SEO writes this page's share preview" (or another SEO plugin's name): set the picture and text in that plugin, which is what Facebook and X read.
• "Your theme or another plugin writes this page's share preview": a post of this type was shown with somebody else's tags in its head, such as your theme's own Open Graph option. Set them there, or switch that option off; the fields come back when a post of this type is next shown with this plugin's tags, or up to an hour after that.

With Add Open Graph and X card tags off, the box says nothing about a share preview at all. Turn it on under Networks → Open Graph Tags to get the fields.