As someone who maintained FOSS libraries pre-AI, I think the frequency might have changed, but large drive-by PRs with thousands of changes happened before too, I've been on the receiving end of those many times. Usually they fundamentally change the architecture too, then the submitter get offended/sad/surprised when you tell them you impossibly could accept it and they should stop wasting their time contributing without discussing first. Usually ends with some threats how their fork will take all the contributors or something like that.

What I don't get, is why these LLM users aren't asking their LLM for how to contribute and how the project prefers to contribute, and how they can make sure it's accepted? Literally, the very same tools they use to code, can be used to make sure their PR follows all guidelines, from discussions to acceptance of the PR itself, it's right there, they literally just have to prompt for it! Such a lazy group of people.