In the three years the JHSAT looked at there were over 500 helicopter accidents in the NTSB database.
If you look at the actual ICAO Annex 13 reports the NTSB has published there are just nine, between Aug 2001 and August 2009 (so only 0.6% of helicopter accidents get a full report in the US):
Title: Aircraft Accident Report: Midair Collision Over Hudson River, Piper PA-32R-300, N71MC, and Eurocopter AS350BA, N401LH, Near Hoboken, New Jersey, August 8, 2009
NTSB Report Number: AAR-10-05, adopted on 9/14/2010
Title: Aircraft Accident Report: Crash During Approach to Landing of Maryland State Police Aerospatiale SA365N1, N92MD, District Heights, Maryland, September 27, 2008
NTSB Report Number: AAR-09-07, adopted on 10/27/2009
Title: Aircraft Accident Report: Midair Collision of Electronic News Gathering Helicopters KTVK-TV, Eurocopter AS350B2, N613TV, and U.S. Helicopters, Inc., Eurocopter AS350B2, N215TV Phoenix, Arizona July 27, 2007
NTSB Report Number: AAR-09-02, adopted on 1/28/2009
Title: Aviation Accident Brief: Crash into Potomac River, LifeNet, Inc., Eurocopter EC-135 P2, N136LN, Oxon Hill, Maryland, January 10, 2005
NTSB Report Number: AAB-07-04, adopted on 12/4/2007
Title: Aircraft Accident Brief: Crash of Sundance Helicopters, Inc., Aerospatiale AS350BA, N270SH, Near Grand Canyon West Airport, Arizona, September 20, 2003
NTSB Report Number: AAB-07-03, adopted on 10/30/2007
Title: Aviation Accident Report: Weather Encounter and Subsequent Collision into Terrain, Bali Hai Helicopter Tours, Inc., Bell 206B, N16849, Kalaheo, Hawaii, September 24, 2004
NTSB Report Number: AAR-07-03, adopted on 2/13/2007
Title: Aircraft Accident Brief: Weather Encounter and Subsequent Crash into the Pacific Ocean, Heli-USA Airways, Inc., Aerospatiale AS350BA, N355NT, Haena, Hawaii, September 23, 2005
NTSB Report Number: AAB-07-01, adopted on 3/5/2007
Title: Aircraft Accident Report: Controlled Flight into Terrain, Era Aviation, Sikorsky S-76A++, N579EH, Gulf of Mexico About 70 Nautical Miles South-Southeast of Scholes International Airport, Galveston, Texas, March 23, 2004
NTSB Report Number: AAR-06-02, adopted on 3/7/2006
Title: Aircraft Accident Brief: Uncontrolled Descent and Impact with Terrain, Eurocopter AS350-B2 Helicopter, N169PA, Meadview, Arizona, August 10, 2001 NTSB Report Number: AAB-04-02, adopted on 6/3/2004
The JHSAT approach has pulled some common themes together, but apart from highlighting the failings of the NTSB, the JHSAT conclusions have very little credibility.