I have just set up a questionnaire on a Moodle. The questionnaire is set up for separate groups, and the tutors are set up so that they can only see people in groups that they are in.
When filtering the data within the questionnaire, the groups are recognised correctly, however when exporting as a csv file - it has exported everyone's data, not the group that is currently filtered, and includes people's data in groups that the tutor isn't in (and therefore shouldn't see).
Questionnaire version = 3.1.2 (Build - 2016071300)
Moodle version = Moodle 3.1.3+ (Build: 20161125)