Because it was already mentioned that it was a bad call by an internal dev.

> https://news.ycombinator.com/item?id=47573233

> We've been including product tips in PRs created by Copilot coding agent. The goal was to help developers learn new ways to use the agent in their workflow. But hearing the feedback here, and on reflection, this was the wrong judgement call. We won't do something like this again.

Either way, even if it was a mistake, giving the ability to modify someone else's PR without prompt, in any scenario should have been tested, oh I don't know.. At least once.