this is why given a choice between theory/plans/estimates/schedules or, say... reality and iterating and observing what-actually-happens ... I always prefer the latter. in software engineering, in human relationships, and in the physical world around me in general.

Well, sure, as logical people we know that you can't predict failures and that it's always better to play it by ear. Unknown unknowns and all that.

I have worked at several places where salespeople have sold a feature without even asking if it was POSSIBLE, much less created/deployed/tested. "We just sold [Feature X], we told them it'd be ready by [date pulled out of thin air]."