Instructors can create groups of students in portfolio sites to allow filtering the list of matrix/wizard students (see
SAK-10612 and SAK-11545). Unfortunately, the matrix tool does not differentiate between worksite groups and section groups. Both types of groups make use of the same underlying framework, and are only differentiated by the entity's properties (e.g. group_prop_wsetup_created = true).
The changes in
SAK-16261 should also be tested to make sure they're not affected by this problem. Group Filtering in the Evaluations tool should also be reviewed.