When I worked at MSFT, we used to break up (senior) people according to which stage of the project they were better at leading, either as technical ICs or managers. If you chunk projects into four parts: early, build-up, build-out, and release (not the words we used --- we just used numbers 1-4), almost all senior people tend to do best at some close span of two of them. I was personally frequently slotted into 1/2 roles, but I knew lots of others who fit more into 3/4 roles. It's a mixture of personality type and skillset.
Few things can doom a project more quickly than putting a "shipper" in charge of an early-stage project or vice-versa. You end up with management that sends all the wrong signals to the team and everybody can tell is looking forward to some later stage.
Of course, for junior people, it's important to just make sure they get through all of them. Not just to pick up the skills mentioned by other commenters here, but also to see which they're good at for when you want to stretch them with a leadership role, without setting them up for an avoidable failure.
Few things can doom a project more quickly than putting a "shipper" in charge of an early-stage project or vice-versa. You end up with management that sends all the wrong signals to the team and everybody can tell is looking forward to some later stage.
Of course, for junior people, it's important to just make sure they get through all of them. Not just to pick up the skills mentioned by other commenters here, but also to see which they're good at for when you want to stretch them with a leadership role, without setting them up for an avoidable failure.