I want to expand on this post.
The most important component of project management is, with no doubt for me, empathy. It is not plans, not the execution, but the ability to understand the people involved. This is much more important than project planning, because it will be people executing on the plans. Well prepared plans are still important, but they won’t matter if you fail on engaging people performing different tasks. What makes projects interesting is what happens in between those tasks.
Designing standard tasks is predictable, and from a PM point of view, easy. But as soon as you start adding non-related disciplines together, you start navigating a very interesting, make-it-or-break-it world. If people from both disciplines fail to realize that they are actually working on the same solution (but from two perspectives), then you failed as a PM. If you actually zoom in at the border between two tasks, you will notice the border is not clear anymore. If there is empty space, it means trouble. There will be some minor work, that both person A or B will refuse to do, because it was not listed on their duty. And this minor work will be essential for both of them complete their jobs successfully.
That is why it is important, if possible, to foresee some overlap. It may need more costs, but it can prevent many issues down the road.
The reason for that are the borders of the tasks. They don’t have clear borders. Each situation is different and it really depends on the case when a tasks starts and ends. And it is impossible to to foresee in advance the exact expanse of the task. I think we should talk more about a probably of a task border. Let’s call it probability horizon. Unknown, more vaguely defined tasks will have broader horizons, clear, standard tasks will have smaller horizons. In the first tasks you need broader overlapping, in the second narrower.
The width of the probability horizon depends on correct planning. But for that you must understand the person executing it, because the second they say “that is not for me to do” or “this is not my duty”, you lost as a project manager.