The accident pilot's colleagues are reported to have said he had never flown in cloud before.
From the NTSB Update:
According to FAA records, the pilot held an FAA commercial certificate with ratings for helicopter and instrument helicopter, as well as an FAA instructor certificate for flight, instrument, and ground instruction...His most recent flight review, including proficiency training in inadvertent entry into instrument meteorological conditions (IIMC) and unusual attitude recovery, was conducted in a helicopter with EUROSAFETY International on May 8, 2019. The pilot received satisfactory grades for these maneuvers.
At face value, that looks reasonable, but as a few people rightly pointed out, clouds and a hood are different. The stress that this is "real", the disorientation as the ground appears then disappears, the tendancy to turn with no visual cue etc. And of course temperature, mountains and MEAs. As I am reading, this sounds doubly hard in a helicopter.
I did all of my fixed wing instrument training in an aircraft rather than a sim and was lucky enough to find an instructor who was willing to do most of it at night and also some night IMC (I think him not having kids helped). I feel that it helped me tremendously. My most memorable learning moment was during the winter when ATC wouldn't give us our desired departure route at the 5000' MEA over Livermore due to the Oakland arrivals, instead routing us towards Panoche which was a 7000' MEA. The freezing level was 6000'. We knew that wasn't going to work. But the instructor turned it into a brief but effective learning exercise while we were still over an area with a low MDA. As we continued climbing, he got out his flashlight, pointed it at the strut, said "Here, I got it. Look out the window. You don't ever want to see that." We asked for and were quickly granted a 180.