Spin and Aerobatic Flight Instructors who transitioned to Part 61 must demonstrate their competency to a Flight Examiner before exercising the privileges of the spin and/or aerobatic training endorsements.
The reference for that statement is a CASA Instrument which is changed every now and then as it has other requirements – the short paragraph on flight instructor training for flight activity endorsements is buried amongst other stuff and CASA doesn’t promote its existence. See the story at https://aopa.com.au/has-casa-lied-flight-instructors-beware/
This slideshow below assists with that demonstration: