Update doc/api/packages.md

Co-authored-by: Antoine du Hamel <duhamelantoine1995@gmail.com>

Author: marco-ippolito

doc/api/packages.md

@@ -1181,8 +1181,11 @@ The `"private"` field marks a package as private, signaling to package managers
 such as _npm_ that it must not be published to a public registry.
 By default, Node.js refuses to strip types from TypeScript files inside
 `node_modules`. When [`--experimental-strip-private-modules`][] is enabled,
-Node.js allows type stripping for a file only if its `package.json`
-sets `"private": true`.
+Node.js allows type stripping for:
+
+- files that are not descendant of a `node_modules` directory.
+- files that are descendant of a directory whose parent is a `node_modules` directory
+  and that contains a `package.json` file that sets `"private": true`.
 
 [CommonJS]: modules.md
 [Conditional exports]: #conditional-exports