I imagine the example is artificially constructed to fit the flow of the narrative.

Consider that the initial idiom

    const ps = persons
      .map(p => ({ ...p, age: p.age + 1 }))
      .filter(p => p.age >= 30)
      .slice(0, 5);

is not only unoptimized in the sense that it does O(n) age increments, but also does O(n) object clones (which are far more expensive). It also does twice as many array allocation as the naive procedural approach:

    const ps = [];
    for (const p of persons) {
      if (p.age > 29) ps.push(p);
      if (ps.length === 5) break;
    }

If one wants to argue about readability, consider that the lazy approach requires understanding the semantics of both `chain` and `take` (in addition to all the mentioned downsides about extra code), whereas pretty much everything in the procedural approach can be found in a beginners JS course (or most other mainstream languages). And for an advanced developer's eye, the cost of the snippet is explicit.

Takeaway: sometimes, the seemingly overly simplistic solution is the best choice, and conversely an overly complex solution is a product of a semi-irrational bias, rather than objective analysis.