The mandatory bit about accidents is when we must report them. The Regs don't say when the AAIB WILL/must investigate. However, it is pretty obvious that they will almost always invesigate with a fatal. For less serious accidents, they can do a remote investigation, following up on the reporter's evidence. It also seems to make a big difference whether the flight is private or public transport, in terms of their interest. In that respect, they follow the whole regulatory regime.
There is a pretty hefty extra premium for insurance for ab-initio training on a Jetbox. Perhaps this could be one of those accidents explaining why. (I am assuming that this was ab-initio - there is little point in sending a stude solo on a type rating conversion). I was reminded of a similar event recently which occurred maybe 10 years ago at Luton involving a B206. The results were sadly fatal. A MR blade entered the cabin, as I recall, during hover/take-off manoeuvres.