> it's like coming to buy a house and agent says "this house is $200k or $300k but you sign here on the bunch of dotted lines and we'll tell you all about it eventually before you have to cut a check.

Not really with price, but when I've had my house built, the date was overshoot by about 30% too, because of various reasons, like having to stop for winter because some supplies were late by a week several times or my builders had to help teams at other places from time to time (because other teams were late too), not doing anything at my house sometimes for days. So even when building homes (something they do again and again) you can't really put exact estimates.