Wasn’t there a “maintenance mode” directive in wp-config.php?

Sorry, this is kind of a silly question, but I just had to ask:

Recently I’ve had to put a site quickly into maintenance mode, since it was launched before it was “officially” announced, and I didn’t want to install yet another plugin to do so.

I remembered vaguely that there was a directive in wp-config.php that allowed you to put the site in “maintenance mode”, or offline mode or something to that effect. ChatGPT even says that this code can do so:

// Take site offline
define( 'WP_SITE_MAINTENANCE', true );
define( 'WP_SITE_MAINTENANCE_MESSAGE', 'Sorry, we are currently undergoing maintenance. Please check back later.' );

But when seeking confirmation on Google, I haven’t found any docs about it, and of course, no docs about a supposed WP_SITE_MAINTENANCE directive.

We all know that ChatGPT can hallucinate, but am I hallucinating it too? Was there in the past any wp-config.php directive to put WordPress into maintenance mode? Has there ever been?