At the moment, the plugin just displays the WordPress's core Login form when an user visit our user only pages. So, the login form doesn't use Bootstrap markups to get styled. There is already a plan to introduce our own Login/Registration system. Until then, the better solution would be to use a "Third Party Registration" plugin called "Ultimate Member" and configure our user only pages to show only for registered users. So, the "Ultimate Member" plugin will display it's own beautifully styled login form when a guest user visit these pages.
Hope, this helped you.