Name filled in at registration not synced with civicrm

Instead of the standard WP registration form I use a plugin (User Registration from wpeverest). Their registration form allows to immediately let the user fill in some more information such as firstname, lastname,…

When a user is registered in this way, a contact is created in CiviCRM, so far so good, but firstname lastname isn’t synced. It takes only the emailadress (and the username as nickname).

Is this behaviour to be expected?
What can I do to make it sync also firstname lastname?

Plugin works fine further. Contact in Civi is created, and if an update is done to the WP user Civi contact is also updated, also in the other direction, so the problem is only at registration itself.