Occam's Razor indeed Melmoth.
The only bit of evidence supporting a hypothesis of a certain type of Stealth Helicopter appeared during an otherwise highly classified operation in a politically complex area and where indeed such an alleged capability could arguably provide deniable cover for other cooperating agencies.
So with no verifiable collateral supporting information before or since over many years, would not the simplest explanation be that it never existed,as such, in the first place?