The one on the top right and at the bottom of each topic page is the topic admin wrench. it allows you staff functions on the topic.
While the wrench below each post is the post admin wrench - for staff functions specific to posts only.
Combining the two doesn’t really make sense. I think what is confusing you is that they are both wrenches and expect the same menu; the wrench is a generally universal admin function icon we use in other places, like for category admin on category pages, user account admin on profiles, for example.
Perhaps just think of the wrench as an admin button for any part of Discourse, so when you see it, you know you can change something about that section or perform staff-only related functions.