What it sends to browsers and search engines

• Status 503 Service Unavailable (or 200 for Coming Soon, if you chose it), plus Retry-After
• Cache-Control: no-store, so caches don't keep the page
• X-Robots-Tag: noindex and X-Content-Type-Options: nosniff

The extension never reads or writes .htaccess or any other server configuration file. Everything happens inside Joomla.