They are saying it is a heavily modified MH-60, seems like it actually would be a completely new aircraft since the only thing likely the same would be the engines.
What is "pure stealth"? everything can be heard to a certain extent and everything can be detected, the reduction of the RCS is the thing that makes something "stealth". Nothing is invisible to radar but it may be extremely small on it.
Tom Clancy had a book a few years ago that used the H-66, highlighting the fact that while the F-22s have a very small RCS, they still move at fast speeds which radar could still scan for. Helos, on the other hand, could have a dramatically reduced RCS and move at a slower speed to avoid computer filtering.
I know, fiction, but an interesting fiction nonetheless.