How to justify the PM problem of switching from task to task?

Question

Project management

Colleagues, what links to leave the PMU to let him understand why it is physically difficult for programmers to "quickly" be distracted by something?
I know about the "stream", about the "crystal castles", but I am primarily interested in books with some authoritative authors, where this problem is described.

Answer 1

no way, the PM needs to be told the time it takes to complete the task, everything else is not his responsibility, you specify the start and end of work, everything else is in the same order
if you need to work on two tasks, then you specify which task has a higher priority, and work on it, saying that the second task will be started after the first one is completed