Well, "rename variable" is a pretty easy refactoring to get right and review when made in a separate commit :)

I wouldn't say I care *really* strongly, but OTOH it's a well-known and pragmatic approach to refactoring of an existing codebase:

1. Don't ever attempt a "big bang" refactoring because that's too risky (and noone has time to do that anyway). 
2. But when you notice smells in the code which you are touching in order to fix / add functionality, that is the ideal time to fix the smells via refactoring.  Because realistically if you don't do it then, it will never happen.