While it's simple to run NextJS as a simple Node process that server-renders everything it's not trivial to run it in the way the Vercel does, including running middlewares specifically on a different edge runtime (as well as supporting the `export const runtime = "edge"` directives); incremental static regeneration (statically pre-rendering some set of routes at build time and then hosting them as static files from a CDN rather than computing them at request time), and so on.

I'm guessing this solution doesn't really do that stuff, but for many apps it's not a big deal if it doesn't.