Keanu spent 8 hours a day for months doing one thing. You can bet your bottom dollar that the director, Stahelski, didn't do that; and that if he had, the movie wouldn't have been a success.

I think the proper recognition here is that there are different kinds of work. In order to scale past a single person, there needs to be coordination work; the work of coordination necessarily means that someone throws a ball to you, you ponder it briefly, and then toss it to someone else. The deep, full-throttled, do-only-one-thing kind of work that Keanu did was made possible by the juggle-dozens-of-obligations work that Stahelski and the other support staff did. Division of labor: Stahelski juggled the balls so that Keanu could focus.

I think where this breaks down is where managers don't realize these different kinds of work. They must juggle lots of balls; this kind of juggling is necessary for scale; and usually people who do well as managers actually like the juggling at some level. So they naturally project that onto the people working for them. Whereas the ideal manager will recognize that their primary job is to juggle balls so that their stars can do a completely different kind of work than they do.