Allow logins to WordPress while "maintenance" mode is engaged.
Imagine being able to perform actual maintenance, when "maintenance mode" is engaged... Instead, actual maintenance can only be done with a 3rd party extension. Or, consider changing the labeling of "maintenance mode" to "WordPress On/Off" since engaging maintenance mode prevents actual maintenance, prevents logging in, and just shuts down the site.
This ability was added to WordPress Toolkit v5.7. You can turn it off in maintenance mode settings, if you wish so.