Activity completion reports filter by first name and surname not working with custom profile fields

Prerequisites: Users with different names (not starting with the same first or last initial) Test: Log in as admin. Go to site administration >> Users >> User profile fields and then create a custom profile field with text input type and make sure that the character limit is < 256 characters. Go to site administration >> Users >> User policies. In Show user identity, tick your custom profile field. Create a course, thereby making sure to have activity completion enabled, enrol a teacher and some students and create some activities that can be graded, e.g. assignments or tests. Make sure that the student's first names and last names do differ in their initial letter. As a student, go and complete an activity. As teacher, go to course reports and then click Activity completion. Note: Activity completion only appears if there are assignments that students have completed. Try to use the filter for firstname and lastname to show only a subset of the students. Verify the users are correctly filtered.