Update lazy.md to mention default exports (#6285)

React.lazy dots into the `default` property. Document this.

Author: sophiebits

src/content/reference/react/lazy.md

@@ -32,7 +32,7 @@ const MarkdownPreview = lazy(() => import('./MarkdownPreview.js'));
 
 #### Parameters {/*parameters*/}
 
-* `load`: A function that returns a [Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) or another *thenable* (a Promise-like object with a `then` method). React will not call `load` until the first time you attempt to render the returned component. After React first calls `load`, it will wait for it to resolve, and then render the resolved value as a React component. Both the returned Promise and the Promise's resolved value will be cached, so React will not call `load` more than once. If the Promise rejects, React will `throw` the rejection reason for the nearest Error Boundary to handle.
+* `load`: A function that returns a [Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) or another *thenable* (a Promise-like object with a `then` method). React will not call `load` until the first time you attempt to render the returned component. After React first calls `load`, it will wait for it to resolve, and then render the resolved value's `.default` as a React component. Both the returned Promise and the Promise's resolved value will be cached, so React will not call `load` more than once. If the Promise rejects, React will `throw` the rejection reason for the nearest Error Boundary to handle.
 
 #### Returns {/*returns*/}
 
@@ -48,7 +48,7 @@ const MarkdownPreview = lazy(() => import('./MarkdownPreview.js'));
 
 #### Returns {/*load-returns*/}
 
-You need to return a [Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) or some other *thenable* (a Promise-like object with a `then` method). It needs to eventually resolve to a valid React component type, such as a function, [`memo`](/reference/react/memo), or a [`forwardRef`](/reference/react/forwardRef) component.
+You need to return a [Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) or some other *thenable* (a Promise-like object with a `then` method). It needs to eventually resolve to an object whose `.default` property is a valid React component type, such as a function, [`memo`](/reference/react/memo), or a [`forwardRef`](/reference/react/forwardRef) component.
 
 ---
 
@@ -70,7 +70,7 @@ import { lazy } from 'react';
 const MarkdownPreview = lazy(() => import('./MarkdownPreview.js'));
 ```
 
-This code relies on [dynamic `import()`,](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/import) which might require support from your bundler or framework.
+This code relies on [dynamic `import()`,](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/import) which might require support from your bundler or framework. Using this pattern requires that the lazy component you're importing was exported as the `default` export.
 
 Now that your component's code loads on demand, you also need to specify what should be displayed while it is loading. You can do this by wrapping the lazy component or any of its parents into a [`<Suspense>`](/reference/react/Suspense) boundary: