Preview changes on published post shows saved version

I’ve changed my preview button to link to a replica of the page my blog is embedded in. That page pulls in all published posts as well as the top draft.

When I preview changes to a draft, the page shows the changes to the draft.

However, previewing edits to published posts only shows the published version.

The link does read as
https://example.com/test_page.php?p=15&preview=true

But this doesn’t seem to make any difference regarding changes to the published posts.

Help please?

The published posts section uses this retrieval code.

$posts = query_posts(array('p'=>$_GET['p'], 'posts_per_page'=>10, 'order'=>'DESC', 'post_status'=>'publish'));
foreach ($posts as $post) : setup_postdata( $post ); ?> Etc Etc Etc

The draft section uses the same except post_status = draft.