I knew that the trend for Manager READMEs bothered me, but this really helped me to nail down why. When I'm wearing a manager hat, I see it as my job to serve the people who work for me. But READMEs are a one-way communication medium. They send the message, "It's your job to pay attention to me, the manager. You must learn and conform to my quirks." I think that's exactly the wrong message for a new employee.
This post is written by the author of The Manager's Path, which I also recommend: https://www.amazon.com/Managers-Path-Leaders-Navigating-Grow...