It took me a number of edit tests to figure out what these buttons did, because they never seemed to change anything. Specifically, I realised that they expand or collapse blocks of text that aren't part of the edit conflict, but text isn't collapsed unless it reaches a certain length. So if you have an edit conflict that only has one or two (or no) other sentences of text, the buttons appear to do nothing. I'd propose changing the behaviour so that the buttons only show when some text has been collapsed to avoid confusion.
Topic on Help talk:Two Column Edit Conflict View
'Unchanged text' buttons behaviour is sometimes confusing
Thanks a lot for your feedback, in particular your description of your assumptions and observations while you tried to use the function – this helps us a lot to understand how we might tackle this. I filed an issue on phabricator, so we can consider the usability problem you uncovered.
@Samwalton9 just making sure: You are talking about the radio buttons above the text area, not the expand/collapse buttons within the text area, right? Thanks again for all your feedback!
Yes, the radio buttons :)