Global CSS (import "tailwindcss/tailwind.css") shouldn't be importable in a layout component

[fnick851]

What version of Next.js are you using?

10.0.5

What version of Node.js are you using?

14.15.4

What browser are you using?

Chrome Canary

What operating system are you using?

macOS Big Sur

How are you deploying your application?

Vercel

Describe the Bug

In the doc, it is said that "In Next.js, you can add global CSS files by importing them from pages/_app.js. You cannot import global CSS anywhere else."

With the "/styles/globals.css" this is indeed the case - it will emit an error. But I can import "tailwindcss/tailwind.css" in a layout.js component. Shouldn't "tailwindcss/tailwind.css" also be considered global CSS and only importable in _app.js component?

Expected Behavior

Emit an error when importing "tailwindcss/tailwind.css" in places other than _app.js.

To Reproduce

Import "tailwindcss/tailwind.css" in any places.

1. Scaffold a next.js app
2. Set up tailwindcss
3. Import "tailwindcss/tailwind.css" in any component other than _app.js