Setting Advanced Attributes for Admin Columns via MB Builder

Hi, I'm having trouble creating an admin column for a custom taxonomy term. Using the docs from:
https://docs.metabox.io/extensions/meta-box-builder/
https://docs.metabox.io/extensions/mb-admin-columns/

The taxonomy term is created manually in my theme (it was created before I started using the MB plugin).

Using the MB Builder to add a custom meta field to the term.

When I add the advanced attribute using the dot notation:

Advanced attribute key: admin_columns.0.position
Advanced attribute value: before name

Advanced attribute key: admin_columns.0.sort
Advanced attribute value: 1

The generated code for the field array looks like:

'fields' => array(
            
            array (
                'id' => 'custom_order',
                'type' => 'number',
                'name' => 'Order',
                'step' => 1,
                'required' => 1,
                'label_description' => 'Specify the order in which the Player Positions will be displayed.',
                'admin_columns' => 
                array (
                    0 => 
                    array (
                        'position' => 'before name',
                        'sort' => 1,
                    ),
                ),
            ),
        ),

When I use JSON:

Advanced attribute key: admin_columns
Advanced attribute value: [{"position":"before name","sort":"1"}]

The generated code for the field array looks like:

'fields' => array(
            
            array (
                'id' => 'custom_order',
                'type' => 'number',
                'name' => 'Order',
                'step' => 1,
                'required' => 1,
                'label_description' => 'Specify the order in which the Player Positions will be displayed.',
                'admin_columns' => 
                array (
                    0 => 
                    array (
                        'position' => 'before name',
                        'sort' => '1',
                    ),
                ),
            ),
        ),

In both cases the admin_columns array is nested a level too deep. What am I doing wrong?
Thanks in advance.