It does post to wp-login.php, there’s no need to re-invent the wheel and re-write the WordPress login process.
However, if you enable the ‘block wp-login.php’ feature, it puts a line in the .htaccess file to block direct access to that file(it does this via referrer with exceptions for the mobile apps).
In addition, the Login form is generated via javascript, so it does not exist on the page until the correct function is run to generate it.
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So, could someone spoof the referrer and still access wp-login.php? yes! Is this something done normally? no! So, this plugin certainly makes WordPress more Secure than normal. That’s all I can do. There are plenty of other Security plugins which specifically target bots and blocking them, this is not that plugin. The goal is to ‘Hide’ the normal site Login, and it does that very well.