Value of Default Category doesn't gets renamed

1.Create a category.
2.Create a course in that category.
3.Now edit the name of category that was created in step -1.

We will notice that if in 1st step the category created is Test and course is moodle there exists a category named Test in Question bank which has Default Category as "Default for Test".

Now when we change value of Test to Test-1, the category name changes to Test-1 but the value of Default Category is still same "Default for Test" in Question bank.
It doesn't gets changed.