OK.

But that should be done later in the process. I'd rather an LLM auto-reject my application vs spending 5 hours on a writing exercise.

Think about, I apply to a minimum of 5 jobs per day. If I need to spend 5 hours for each application I'm spending 25 hours a day on job applications. Obviously this isn't possible.

I think that you are (naturally) approaching it from your side, and they're (naturally) approaching it from theirs, and it sounds like it's not a fit. That's a successful outcome for a hiring process.