That's just a regional/educational quirk. Classically-educated folks and older Brits are both quite likely to use the "needs no" version.

Most "LLM voice" quirks come from actual human writing styles, even if Claude et al have managed to distil those styles into something pretty horrific.

On the other hand, the way you can tell the title line was at least edited by a human, is the missing comma before "and needs no system prompt".

A human could write either. The former is just slightly more formal and concise.

Before AI, I used to write everything in somewhat formal phrasing mostly because I enjoyed it and a tiny bit because I assumed (perhaps incorrectly) that it made me sound smarter. Post-ChatGPT, I noticed that most LLMs had a writing style fairly similar to my own, so I changed my writing style to appear less formal in most circumstances. While I'm not anti-AI, I'm always fearful of being mistaken for a bot.

Depends on the human.

I would use that turn of phrase (needs no XYZ) — but maybe not in the context of system prompts, perhaps. Though I don't know; sometimes a flourish is a nice thing.

You might be right that the clash of that vernacular pattern and technical language is a "tell", but AI did learn this stuff from actual people; a lot of the time Claude reminds me of an actual person who worked for a firm I worked for in the 90s, who wrote in an annoyingly gnome-wizard style.

Ultimately it's the volume of these problems that is the tell.

Does ESL user write like human to you, even though they could make a mistake?