Another comment: the only vicious and totally-unexpected spin
entry I ever...

Well that sounds horrible! Are pylon powered sailplane
manufacturers required to demonstrate spin recovery with the
engine out and stopped?

Not flown a Ventus M of any type but this looks like another
example of poor systems design. If the engine retraction sequence
consists of switching off ONE switch (e.g. DG808) or moving one
lever (Antares) then the pilot has nothing to do but control the
airspeed. Many of these other self launch/turbo retract systems
look like an invitation to "finger trouble".