There's a big difference between a well considered high quality contribution made using AI as a tool and "claude find and fix an issue in this repo so I can put on my resume that I contributed to a high profile project". The problem is that it takes considerable time of the reviewers to filter out the high quality contributions vs the low quality ones.

I do think closing off contributions is a big step and would rather most projects find a middle ground, but it's definitely understandable why they did this.