"Moving" a product to a category in Commerce Manager doesn't set as Primary category

Description

Steps to reproduce

1. Go to Commerce Manager > Catalog Management > edit a variant item.
2. In the Relations tab, remove the relation and save the change. The item doesn't have relation.
3. Move the item to another category folder.
4. Go to the Commerce UI and click the [Belongs To] tab.

Expected:
The category is set as Primary Category.

Actual:
The category is set to the [Additional Categories] section.