Category-context questions are copied to course-context, why?

Hello,

I'm having a problem, why is question categories copied to course-context when they are originally in category-context with Administrator-rights?

I have tested with Moodle 3.1, 3.5 and 3.8.

Error message per category is following; 

"The questions category "0 Oletus kohteelle Technology", originally at system/course category context in backup file, will be created at course context by restore

"The questions category "cars", originally at system/course category context in backup file, will be created at course context by restore

Why is backup reverting to fallback when I'm doing this as an administrator

Steps to repeat

1. I create Quiz on a course1 in category1
2. I add an question to the quiz from this category level questionbank category called category1
3. I create a course2 
4. I use import to import Quiz from course1
5. I get an warning: "The questions category "0 Oletus kohteelle Teknologia", originally at system/course category context in backup file, will be created at course context by restore
6. Questions are restores to course-context and they do not stay in category-context.