Agile isn't meant to imply speed in the sense of LoC/s, though right? The speed in Agile is about getting customer feedback sooner rather than later (so maybe a kind of latency?). I don't think sprints are mentioned in the Agile manifesto or related materials.
And even within frameworks like Scrum, I don't think that "sprint" was ever intended to mean that programmers are supposed to be in permanent crunch mode.
And even within frameworks like Scrum, I don't think that "sprint" was ever intended to mean that programmers are supposed to be in permanent crunch mode.