Feed root category products aren't displayed in RSS

[marispulk]

Bug description
Products inside RSS feed root category are not displayed in RSS feed. Displays only products that are in subcategories.

Steps for reproducing
Steps to reproduce the behavior:

1. Go to 'magento2.smaily.dev admin panel
2. Click on Catalog -> Categories
3. Click on root category "Sokid". Scroll down to "Products in Category". You can see product inside this category(Tüdrukute müts Cassie).
4. Click on subcategory "Rohelised sokid". Scroll down to "Products in Category". You can see product inside this category(Sall "Murphy").
5. Generate RSS feed from "Sokid": http://magento2.smaily.dev/smaily/rss/feed/category/sokid
6. Generate RSS feed from "Rohelised sokid": http://magento2.smaily.dev/smaily/rss/feed/category/rohelised%20sokid
7. "Sokid" RSS displays only 'Sall "Murpfy"' but not "Tüdrukute müts Cassie".

Expected behavior
RSS displays both: products from feed root category and subcategory(s), if feed root category is chosen for feed.

Actual behavior
RSS feed displays only products that are in subcategories.

Magento version
Version 2.3.6

Module version
Version 1.0.2