Meh, you're just contriving extreme circumstances for your analogy so that the software developer is both a super hero and has no blame in being late with deliverables.

There are simple methods to combat gross inaccuracies in the client specification. You document the requirements for what you'll be delivering in a carefully worded Statement of Work that the client signs off on, you ask to be paid in chunks as you go with a portion up front, and you implement a system of change control so that it's totally clear if the customer is sending you off in a completely new direction. At that point, you book what you've worked at your hourly rate and you submit new work and time estimates for the changes.