The idea here is just to be precise in what we're communicating, when providing a forecast, because different departments have different risk tolerances on that

The idea here is just to be precise in what we're communicating, when providing a forecast, because different departments have different risk tolerances on that forecast. What the lognormal says is "it might even be done by late May, most likely by June, but almost certainly by December". The dev department needs to allocate people, so for them, the most useful thing is the mean completion time. So for them, June is the important thing, although they want to be aware of potential delays in case they need to reshuffle. The sales department is playing a very different game. Upset, impatient customers cost a lot, both in terms of sales and reputation, and can be very unforgiving. Sales much prefers to communicate a hugely pessimistic version of when something will be ready, that they have confidence in, and possibly be early, rather than a 50-50 estimate. This is decision theory in action, where each actor combines the same probability distribution with different payoff matrices and so arrives at different conclusions suitable to their role. To enable this, we clarified the language around "estimates", "commitments", and "promises", as shorthand for different intervals of the same underlying distribution.