Our configuration settings (show on login page) allow to choose to show the Social Login on action login_form, which is after the inputs, as your image shows. However, we define a oa_social_login action hook, that you can call (do_action) at the required place. It also supports short codes. So, maybe you try to use that hook (and perhaps disable the show on login page setting) to place it where you want on your custom login form.
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