Is there any reason this is better than just reading your regular readme or docs?

All of these things look helpful for humans too!

The main difference between AGENTS.md and a README.md is that coding agents will automatically ingest AGENTS.md when they start.

You may not want them to ingest README.md if it's long and contains irrelevant information as that might be a waste of valuable tokens.

You could say that a Readme is declarative, while an agent file is imperative.