In terms of performance, the Zen 2 sample is almost as fast as Intel's Core i7-8700K. The bad news is that it still crashes all the time, the current sample is far from stable.
The forum member claims RTG is getting early access to the sample because of some changes to some unidentified interconnect that require modifications to the video drivers, to make them work better with the Zen 2 processors. The forum post was published over two weeks ago, but wasn't picked up by tech media until this weekend.