Unless AAC flying grading has changed recently it still aims to grade applicants for suitability (or otherwise) to attend the full Army Pilots Course, ie try to weed out the probable failures and the training risks prior to loading on an expensive flying course.
None of the 13 flying hours are solo as each exercise is designed to allow the student to demonstrate to the instructor an ability to learn and fly each exercise to a satisfactory standard in the limited flying time available. A solo sortie would be difficult to grade so is therefore not part of the grading course.
Generally students solo within 8 hours of starting the full course.
Good luck to them both and hope to see them at Wattisham, now, any sons and daughters of our politicians like to have a go?