It’s teaching them in the first place. You can’t teach an LLM. Writing a heap of AGENTS.md is not teaching. LLMs take it as information, but they don’t learn from it in any non-superficial sense.
With https://code.claude.com/docs/en/skills you kinda can teach new things. And also, I have little doubt Anthropic reads these and future AIs might get trained on the most popular recommendations.
Yes, it's a crutch. But maybe the whole NNs that can code and we don't really know why is too.
Actually you can. Training data, then the way you describe the task, goals, checkpoints, etc is still training.