Yes, presumably to run the build as a user which is as unprivileged as possible. Which is a reasonable idea, though it might seem paranoid in today's `curl | sudo sh` world.
I actually really like the authenticity and humility of DJB including that in the instructions. I think it's likely many people trust his code (and he's certainly written a lot of extremely security sensitive stuff), but of course it's a much better practice to not trust him quite so much.
Really? This is software where the author named it after himself, claims that it holds a new speed record with no comparisons benchmarks (just references a single number from a paper in 2015), uses the word "easily" FOUR times in the limitation-section without any links or explanations, and doesn't reference any other libraries/resources/software/solutions.
Authenticity, sure. Humility - not after his approach to the students issue in recent years where he was more interested in being correct then helping people :-(
I was talking to another person in the community, now this was well over a decade ago, maybe two, with the initials "DJB". He said: "I went onto IRC once. I was mistaken for Daniel Bernstein. It was the most awful 15 minutes of my life."
I spoke to another fairly famous person a few years later, let's say author of the authoritative book on one of the alternatives for one of djb's software packages. He said something along the lines of: It's a shame djb gets along so poorly with other people, because he has a lot of good ideas.