The auto created relationship has an extra taxonomy in it?

Hello, I am having an issue setting a relationship programatically and when I looked in the code I saw that there is 'taxonomy' => 'category' being added, is this right? / Do you know why this is appearing?

<?php
add_action( 'mb_relationships_init', 'your_prefix_function_name' );

function your_prefix_function_name() {
    MB_Relationships_API::register( [
        'id'         => 'university_user',
        'reciprocal' => true,
        'from'       => [
            'object_type'  => 'post',
            'post_type'    => 'university',
            'admin_column' => [
                'position' => 'after tags',
                'link'     => 'view',
            ],
            'meta_box'     => [
                'title' => 'User',
            ],
            'field'        => [
                'query_args' => [
                    'orderby' => 'title',
                    'order'   => 'ASC',
                ],
                'max_clone'  => '1',
            ],
        ],
        'to'         => [
            'object_type' => 'user',
            'post_type'   => 'post',
            'taxonomy'    => 'category', //Is this needed? 
            'meta_box'    => [
                'title'    => 'University / Institution',
                'priority' => 'high',
            ],
            'field'       => [
                'query_args' => [
                    'orderby' => 'title',
                    'order'   => 'ASC',
                ],
            ],
        ],
    ] );
}