A HUGE amount of the workday artifacts engineers have been forced to produce since we started the internet is project estimation documents for our managers. The training corpus on this stuff is immense and now all ingested in to these models. It’s doing no thinking at all when it gives you an estimate, it’s matching correlated strings which the humans of the past had to write down.
Fun fact, all those human-sourced estimates were hallucinations too.
It would be very surprising if the AI training corpus includes a lot of project estimation documentation, since most of those are confidential and not publicly available.