In Next.js v12 it's possible to set a page to use the Edge Runtime for SSR? How?

Question

I'm using v12.3.4

I noticed that the page router version of this doc Rendering > Edge and Node.js Runtimes, don't explain how to do it, the app router version instruct to set export const runtime = 'edge' on the page.

I try that, but in Vercel it renders the page with type "Serverless function" instead of "Edge function".