Steps to reproduce:
============
1. put a course into separated groups mode
2. create two groups BOYS and GIRLS
3. add users Boy1 and Boy2 into BOYS, add Girl1 and Girl2 into GIRLS
4. log in as Boy1
5. go to Full report of recent activity and select Advanced search
6. check the field Participants

What I expected:
===========
As the mode is set to separated groups for both course and module, I should see only users from my group, i.e. Boy1 and Boy2

What happened:
===========
I can see all users in the course - even the members of GIRLS