Historical order data - explanation required

[sanddweller]

This issue is about https://kb.x-cart.com/modules/order_reports.html (source file: https://github.com/xcart/xcart-docs/blob/master/_pages/kb_en/modules/order_reports.md)

The information presented on the page needs more detail about how historical orders are presented.
For example, if a product within a historical order has been deleted, or has changed category, then how is this product presented in the Grouped by Categories report? What of products that have no category assignment?