Verify canary release

• I verified that the issue exists in the latest Next.js canary release

Provide environment information

Operating System:
      Platform: win32
      Arch: x64
      Version: Windows 10 Home
    Binaries:
      Node: 18.16.0
      npm: N/A
      Yarn: N/A
      pnpm: 8.4.0
    Relevant packages:
      next: 13.4.4-canary.3
      eslint-config-next: 13.3.0
      react: 18.2.0
      react-dom: 18.2.0
      typescript: 5.0.2

Which area(s) of Next.js are affected? (leave empty if unsure)

App directory (appDir: true), Routing (next/router, next/navigation, next/link)

Link to the code that reproduces this issue or a replay of the bug

https://github.com/Djboy08/nextjs-bug

To Reproduce

BASED ON REPO:
you can see the normal route which is not using static stuff, and theres a bugged route, which is using static stuff.

Bugged route wont ever show the loading screen.

In order to reproduce simply create a blocking RSC page that is static in some form, i.e dynamic = 'force-static' or generateStaticParams in a dynamic route.

If the dynamic page with a slug has not been compiled yet, a loading.tsx or suspense won't show in order to wait for the initial build of the page. As well as a loading.tsx does not show if your navigating to a already compiled/cached page and theres a latency of any kind, a loading.tsx won't show..

Describe the Bug

The bug causes dynamic routes that are trying to use ISR to cache the dynamic pages to serve on next request to not show loading.tsx/suspense fallback on first request and on minor latency or delays while the static page is loading itself.

If you have a slow internet connection loading.tsx should still show up regardless if its a static route because the route may be slow and we want something to fill the area.

Secondly, loading.tsx/suspense should atleast show on the first request since there is not a compiled page yet. In a case where a static dynamic page takes 5 seconds to compile, the website just blocks until its done.

Expected Behavior

The expected behavior is that a suspense fallback or loading file should show up on static files that are happening at runtime for
A. the first request that causes the page to be compiled and cached (which takes time)
B. any subsequent request that due to internet connection may cause the page take time to fetch the page.

Which browser are you using? (if relevant)

Edge

How are you deploying your application? (if relevant)

Vercel