Reviewing pull requests that two or more changes have been made in a single file, some times, is not that simple. Even more when those changes aim the same section of code.
So, if each modified file in the pull request interface could have their related commits grouped in a (header or footer) section next to them, the reviewing task could become easier, considering that the reviewer could fetch the related commits for the evaluated file such that he/she could better understand the code "evolution".