Hey @brielov,
I’ve just tested this and, as we would expect, existing files are not overwritten by redirect rules such as these.
Are you sure that your deployed site features the sitemap and robots.txt files?
Could you provide me with your site name and/or API ID, please (both of which are safe to share publicly) for me to take a further look?
If push comes to shove, given netlify.toml’s rule processing order, it’s possible to add a rule similar to this which would get processed before the overarching ‘all-to-index’ rule for a single page site.