I would say it's not intensity alone, but intensity towards a vision. Working hard by itself is never enough, but working hard to create something valuable, that only you can see requires intensity.

A lot of people don't realize they want something until they've seen it. So founders have intensity, and vision for a need only they can see.

Imagine that slow-paced DMV with a lot of intensity, but towards nothing at all. In that case, the vision should be efficiency (without burning out employees).