Not compatible with headless wp setup

I have setup these in my wp-config.php

define( 'WP_SITEURL', 'https://api.mydomain.com' );
define( 'WP_HOME',    'https://www.mydomain.com' );

When the plugin is active the login form posts at the WP_HOME url instead of the WP_SITEURL, thus I cannot login.