The only variant of the T67 which I've spun is the T67A. It was critical to ensure that the weight limits were strictly observed and we had to be VERY careful when refuelling the aircraft to ensure that the actual weight of the crew was taken into account.
The T67A fuel tank is well forward, so with a chubby student the maximum fuel load was quite low and the CG was correspondingly aft, which made the spin less pleasant, but still entirely predictable. I never doubted that the aircraft would recover using the correct technique. Later versions of the aircraft have totally different limitations, but there is no reason to doubt that the spin recovery would be anything but predictable if carried out in accordance with the POH technique
However, some versions of the T67 do seem to have had rudder control restriction issues, hence ADs were raised to ensure that the rudder pedals weren't obstructed in any way. Of course the normal taxying check should be sufficient to ensure that full and free rudder movement is available - does everyone still do that though? I hope so..
Currently, there is no requirement for a PPL holder to hold an aerobatic rating in order to conduct aeros on the T67. But proper training is very firmly recommended - and will become mandatory after Apr 2018.
As with the G-BLTV accident, I suspect that the cause of this sad accident will never be established beyond all reasonable doubt.