My guess: projects "learn" every time we improve documentation, add static analysis, write tests, make the API's clearer, and so on. Once newly started agents onboard by reading AGENTS.md, they're a bit "smarter" than before.

Maybe there's a threshold where improvements become easy, depending on the LLM and the project?

As a hobbyist programmer, I feel like I've been promoted to pointy-haired boss.