When I add an assignment, the category selector contains pages, emails, functions, variables ....
https://prnt.sc/stu4ib
Checking on Same Course:
http://prntscr.com/su82zr
Trying to select Unit Category but these values are not showing up. Can you please, let me know how can I replicate the same
Yes, you are right. tested the same on our demo as well.
And found that it is actually fetching all the recorded activities here in category section
That's why you can see appointments related activity as well
Marking this as a bug
If you want I can hide this via custom CSS(the category part)