Hi there,
Currently, those fields will always shown when you registering on the site as we have this settings
http://take.ms/tLBfL where your users can left it blank and will always use username instead.
if you required them to not shown during registration, you need to do some hacks on the cores file itself ->
/media/com_easysocial/apps/fields/user/joomla_fullname/joomla_fullname.php. Maybe you can try to use attached file and see how it goes.
Note that, you need to replace this files in the future if you update/upgrade your Easysocial as those fixes are done on cores files. And this hack cannot be overridden using template override.
Please do backup this files and re-upload them once you upgrade your Easysocial. Please give it a try and see how it goes.