Goldratt is suggesting in Critical Chain that you convince people to give accurate estimates (as in 50% confidence) instead of building in safety. He’s asserting that this fixes your problem with estimates only ever being under instead of over.

But I just finished the book a couple days ago and I’m still trying to wrap my head around how on earth you’d pull that off in software. Doesn’t work with Scrum at all, and management has to be 100% on board or the betrayal when people get punished for “bad” estimates will destroy the company. I’ve only had that kind of trust one time. And maybe half of that level a couple others.

Among other things the reasoning is this: if you give someone two weeks to finish something that takes “about a week” they will start it a week later and chew up all their safety. And if they complete 4 day tasks in three days they’ll delay delivery because they get punished for asking for more time than they need. And further that a lot of these delays aren’t just procrastination, or funny accounting to work on tech debt off the books (though that does happen IME). Instead it’s the consequence of multiple chains having steps that require the same constrained individual or machine. And trying to reserve that resource when the start dates are up in the air.