Comment by maxbond

Let's say I give you 10 tasks. You're going to have to go back and forth with external stakeholders, and a given task will be blocked much of the time waiting for a response. So you can do each of them concurrently, but it's gunnuh take a year to do each of them.

But the next day I come to you with an 11th task. I tell you this is the only one that matters. I give you full license to blow through your budget, harass people until they get their paperwork done, whatever it takes - this is the only priority. So you get right to work, and with all the blockers cleared you get it done in 6 months.

"Great," I say, "so you can do all them that fast right? And when I come back in 6 months, all of the original 10 tasks will be done?"

But of course they won't be, because you don't have the resources you had before, the external stakeholders aren't as motivated as they were before, and instead of putting all your effort into 1 task you're going to be spreading it across 10.