Even though the documentation mentions the for the mb login shortcode:
'This shortcode shows the normal login form. You can use either this shortcode or the WordPress’s built-in function wp_login_form()'
It seems like the shortcode does not accept all of wp_login_form() parameters such as 'label_password' or 'label_username'.
It'll be really useful to do so, because the fields such as username does accept email as legitimate, isn't that so? It'll be great if we could change the labels via the shortcode to prompt users appropriately.
Additionally, it isn't very useful for us to use wp_login_form when we have chose to use this MB User Profile plugin. One reason is that when using wp_login_form(), any wrong login credentials redirects the user to WordPress's default login page instead of remaining in the custom login page which we are trying to achieve when using this plugin.