doc: highlight module loading difference between import and require

PR-URL: #59815
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>

Author: Ajay-2005

doc/api/esm.md

@@ -332,6 +332,12 @@ syncBuiltinESMExports();
 fs.readFileSync === readFileSync;
 ```
 
+> When importing built-in modules, all the named exports (i.e. properties of the module exports object)
+> are populated even if they are not individually accessed.
+> This can make initial imports of built-in modules slightly slower compared to loading them with
+> `require()` or `process.getBuiltinModule()`, where the module exports object is evaluated immediately,
+> but some of its properties may only be initialized when first accessed individually.
+
 ## `import()` expressions
 
 [Dynamic `import()`][] provides an asynchronous way to import modules. It is