Because it is written before anyone has done any of the work, usually under time pressure, by one person recalling how the last similar job went. Its estimates are the ones the project is judged against for the next six months.
AI planning drafts a project's phases, tasks and estimates from projects of the same shape you have already delivered.
It finds comparable finished projects, uses their actual hours rather than their original estimates, and drafts a structure with a range instead of a single number. Each estimate shows which past projects it came from.
A third integration project of a familiar kind drafts with phases from the previous two, estimated at what they actually cost, with the phase that overran both times flagged.
It will not commit to a date. It proposes a shape and a range; agreeing a deadline is a commercial decision made by people who will be held to it.
Completed projects, their actual logged hours, and how their estimates compared to reality.
It says so rather than guessing, and drafts structure without estimates.
Actuals. Estimates are what were wrong last time.
Yes — it is a draft, and edits are the normal ones.
Fourteen days, every module, no card. Or half an hour with someone who will run it on your own records and tell you where it does not help.