I was intrigued to read the CAA Trainingcom on this topic. A number of years ago I was an instructor at Oxford and we ran a course for screening would-be pilots for a Middle East air force. The course included basic aerobatics but the company policy was that the instructors did not need the aero instructor endorsement as the tuition was not towards an aerobatic rating. I presume that this was agreed by CAA at the time and, indeed, it reflected my interpretation of the relevant section of the Air Navigation Order.
I can only assume that this new interpretation comes from the European/JARS dimension.