You do need to make sure the changes follow the "philosophy" of whatever component is being changed. Otherwise you get things like duplicated functionality or

You do need to make sure the changes follow the "philosophy" of whatever component is being changed. Otherwise you get things like duplicated functionality or APIs that don't have any cohesion. If the Senior engineer frequently works on this specific piece then its not an issue, but no matter how senior someone new to an area will not produce optimal code.