Probably abysmal

Since xslt is built dynamically in the DOM most crawlers don’t build the site and pick up the metadata.

Although I’m not convinced chasing SEO is a useful endeavor any more https://housefresh.com/beware-of-the-google-ai-salesman/

I wonder if AI crawlers would have the same problem and pass over the site

As long as the LLM crawler fetches the XML in the first place I assume it would be fine. Lighthouse is trying to score the rendered HTML, the LLM just needs to understand what's in the document and it can parse the XML directly.