Waterfall was bad due to the excessively long feedback loops (months-to-years from "planning" to "customer gets to see it/ we receive feedback on it"). It was NOT bad because it forced people to think before writing code! That part we should recover, it's not problematic at all.

That's not what's considered waterfall, though. Specs are always required for any work, even if they're only in your head, even if the work takes 15 minutes. It's the length of the feedback loop and the resistance to spec change that makes waterfall, and by his use of tracer bullets I very much doubt it's the case here, if there was any doubt at all to have.

Did you know that agile is just waterfall scaled down to two weeks? Now you know!