Nextend Social Login uses the same HTML elements for the Password field as WordPress does, hence the styling is not done by us but by WordPress.
If the login form specific styles of WordPress are not loaded onto the page, then our password field can look somewhat different, a typical example of this is when you use the Page for register flow setting.
If you want the password field in the custom registration flow to look somewhat similar to the WordPress default password field, you will need to load custom styles, something like this:
To apply this effect only to the page that you selected for our “Page for register flow” setting, you should add it to the page, e.g. via a Custom HTML block.