Why comparing versions is harder than it looks
After an hour of editing, nobody can remember what they changed. You know it feels better. You do not know whether you removed a bullet that was carrying real evidence, or whether the section you tightened lost the one number a screener was going to notice.
So this does two separate things. It diffs the two documents line by line - added, removed, reworded, unchanged - and it scores both versions on the same quality dimensions and shows the movement. The diff tells you what you did. The dimensions tell you what it cost or bought.