As admin search the site settings for "default dashboard" add check that you can add/remove the course overview block from the default /my page. Check that a regular user can go to /my and turn on customization and add/remove the course overview block from their /my page. Check that you cannot add a block that has 'my' => false in its applicable_formats() to /my. For example, block_blog_tags and block_selfcompletion.