The related_categories_mode does not return category data

[wardourdigital]

When I use the related category mode, there is no category data returned.

{!-- Main Entry --}
{exp:channel:entries channel="news" url_title="{segment_2}" track_views="one" dynamic="no" disable="pagination|member_data|trackbacks" status="open|featured"}
	{title}
{/exp:channel:entries}

{!-- Related Cat Mode Loop --}
{exp:channel:entries channel="news|events|media|briefs|partner_content|media" related_categories_mode="yes" limit="3" custom_fields="yes" dynamic="no" url_title="{segment_2}"}
	{title}

        {!-- This does not work --}
	{categories show_group="6|7|8" limit="1"}
		<a class="content-card__category" href="category/{category_url_title}">{category_name}</a>
	{/categories}
	
{/exp:channel:entries}

Describe the solution you'd like
The category data to be returned when using the standard {categories} tag.

Describe alternatives you've considered
I have used the Query add-on to generate the query needed to pull in the category data.

{exp:query sql="SELECT `c`.`cat_id`, `c`.`cat_name`, `c`.`group_id`, `c`.`cat_url_title` FROM (`exp_channel_titles` t) INNER JOIN `exp_category_posts` p ON `p`.`entry_id` = `t`.`entry_id` INNER JOIN `exp_categories` c ON `p`.`cat_id` = `c`.`cat_id` WHERE `c`.`cat_id` IS NOT NULL AND `t`.`site_id` IN (1) AND `t`.`url_title` = '{segment_2}' AND `c`.`group_id` IN (6,7,8) LIMIT 1"}
   <a class="content-card__category" href="{path='category/{cat_url_title}'}">{cat_name}</a>
{/exp:query}

This is very verbose!

Possible solution

I have seen in the mod.channel.php related_category_entries() ln, 4686 if the following is added before $this->parse_channel_entries():

if ($this->enable['categories'] == true) {
            $this->fetch_categories();
}

Then the {categories} tag works as expected. Is there any reason this cannot work?