So, it seems it was a fluke that the above code worked!!
Here’s what actually works (and added a couple of metaboxes too):
function my_remove_meta_boxes() {
if(!current_user_can('administrator')) {
remove_meta_box( 'tagsdiv-post_tag', 'post', 'normal' );
remove_meta_box( 'formatdiv', 'post', 'normal' );
remove_meta_box( 'authordiv', 'post', 'normal' );
remove_meta_box( 'postcustom', 'post', 'normal' );
remove_meta_box( 'trackbacksdiv', 'post', 'normal' );
remove_meta_box( 'linkxfndiv', 'link', 'normal');
remove_meta_box( 'linkadvanceddiv', 'link', 'normal');
}
}
add_action( 'admin_menu', 'my_remove_meta_boxes' );