I'm not sure honestly, if you could raise an issue I'd appreciate it. I didn't go out of my way to do this; it seems to be some default of SvelteKit or the server code that I don't understand?
Seems like something to do with your deployment server config. You may be redirecting all pages to your fallback spa.html. I built the site and served it with `python3 -m http.server --dir build` and it served the script to the browser without an issue.