Export: Matching tag/category slug on simple sites are dropped on export

[samiff]

Steps to reproduce

1. On a WordPress.com simple site, create a new post with the same category and tag (e.g. "Films") assigned to the post.
2. Create a standard export containing that post.

What I expected

• For the export file to contain the post with both assigned terms (i.e. both a "Films" category and tag).

What happened instead

• One of the terms is being dropped.
• On Atomic or WPorg sites, posts with assigned taxonomies that have matching terms/slugs are persisted on export, for example:

<category domain="category" nicename="films"><![CDATA[Films]]></category>
<category domain="post_tag" nicename="films"><![CDATA[Films]]></category>

Context / Source

#user-report 2753304-zen

[tanjoymor]

In the process of doing a manual revert, I found that when the import step was completed, the imported posts had dropped the "Category" when the post also contained a "Tag" of the same name.

Both the Category and the Tag still exist - and on posts that only used one of the two, they remained applied as expected.

It was just on a post where the original copy had both the same Category and Tag applied, that on the import, it only kept the Tag applied.

#3213071-zen

[github-actions]

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