As with most things in life - there are very few absolutes.

It might be convenient to suggest that management is about the here and now and that leadership is about the future.

However, there are many situations where 'managers' must show 'leadership' in their area of responsibility.

A manager who is faced with significant operational challenge in the here and now, for example, must be able to demonstrate leadership to transition his/her area to a new context.

That involves, creating the future vision for his/her area of responsibility, helping  develop the transition plan to achieve it, selling the vision and its benefits to his/her people (and up the organisation) and then steer the transition so that the future vision become the reality.

Similarly, a 'leader' needs to be able to envision, and then deliver it. Just developing a vision is NEVER enough.

In the same way as effective leadership needs to operate equally comfortably in the right-brain and left-brain spaces, a leader needs to be able to see the future and then manage it to realisation. A CEO must do this across the entire organisation, while other executives must do it across their area's of responsibility.

Thus, in most  organisations, effective executives need to display both capabilities. Certainly some executives in some contexts display more of one than the other, but they must have capabilities in both realms to provide overall effectiveness.