Say you have a half-sized team in order for the remaining people to get twice as much time. People working on the project will, on average, be more familiar with the problem. That's not a frequent answer, since most companies are more time-sensitive than budget-sensitive. But that's a good illustration of how budget and timeline are separate things.

That being said, my initial message wasn't about that, but about the idea that plenty of organizational methods abandon tight deadlines in favor of early feedback.

That usually works better when power is decentralized, since the higher you report to, the less people have time to actually look at what you produce (and therefore, the more they rely on low-involvement management methods such as setting deadlines). On the other hand, the more decision power is decentralized to the people actually using the software, the more early feedback will make setting deadlines redundant.