A less charitable take, and something that came to mind for me faster than what others are presenting (that commits fixing bugs that you caused tend to be large

A less charitable take, and something that came to mind for me faster than what others are presenting (that commits fixing bugs that you caused tend to be larger because you know more about the architecture around the code needing to be fixed), is that including other code changes in your bug fix commit serves as a way of covering your ass. If the reviewer needs to sift through and understand 100 lines of whatever (maybe germane to the fix, maybe not), the few lines that address the issue you caused won’t get as much focus, and therefore the issue (that you caused!) itself won’t stand out in your teammates’ minds.