Remove a field from the profile update form but not the registration form

/**
 * This example removes a field (in this example - phone1) from
 * the user profile update. That way, the user cannot update 
 * or change this field after registration.
 */
add_filter( 'wpmem_fields', 'my_remove_profile_field', 10, 2 );
function my_remove_profile_field( $fields, $tag ) {
 
    if ( 'profile' == $tag || 'profile_dashboard' == $tag ) {
        unset( $fields['phone1'] );
    }
     
    return $fields;
}