I'm also an active skydiver. For reference, the AAD (Automatic Activation Device) for a reserve canopy will fire at approximately 750 feet AGL if exceeding a speed of 78mph vertically. This would equate to over 6800 fpm on the VSI and I doubt anyone on here lands a helicopter that aggressively. If interested in how these work, have a search for “Airtec Cypres AAD” which is the most common and prevalent brand. Also of note, is that for most skydiving rigs, the jumper would have to take his rig off to turn off the ADD (without someone else’s assistance) which would be quite difficult in smaller helicopters.
I haven’t read this report, but something went wrong with the AAD or they had a problem with the reserve closing loop.