Why these manoeuvres?
The most exciting outcome was a 1500' altitude loss with inversion and a maximum descent rate of 12,500 fpm
It seems this excursion was not shared.
From the flight-path graphs on the last page of the report it appears there have been ca 10 flights that departed well beyond an aggravated wingdrop plus immediate recovery, resulting in half or full turn spins and picking up high speeds in the recovery with massive altitude loss (average 960 feet).
Although it was not officially reported, I would think it unlikely it was not shared (among flight instructors at least).
While demonstration of "incipient spin", in the sense of a provoked wing drop and immediate recovery, is not uncommon in single engine airplane stall/spin avoidance training, most if not all Airplane Flight Manuals of twins caution against or outright prohibit any asymmetry in combination with stalling.
It's puzzling why in so many stall training flights in the Tecnam Twin the "incipient spin" was exercised. Was it to make a point of perceived critical behaviour (*) of the Tecnam Twin and wanting to secure being current in recovering from it? ... with failiures to do so in ca 10 cases and one fatal? Or were the half and full turn spins deliberately sought? The latter would seem unlikely, if only because no significantly higher initial altitude was used.
(*) Refer to similar accidents with same model