I think we're getting hung up on the concept of dismissing. To question skeptically, to ask if there is evidence or useful context, to seek to learn more is different than to dismiss.

The 5 Step Design Process emphasizes making requirements "less dumb," deleting unnecessary parts or processes, simplifying and optimizing design, accelerating cycle time, and automating only when necessary.

Musk suggests that if you're not adding requirements back at least 10%-15% of the time, you're not deleting enough initially. The percentage is an estimate initially based on experience, and now for several years based on estimates from manufacturing practice.