Nassereith - Obsteig, Austria

Because of a post on another forum, and having checked with the CC  European Guide it recommends not using this road. I just wondered why this was as I used that road going towards the Fern Pass in 2009. We were staying at Stams and so that route was the most direct. Coming in the opposite direction the road does have some steep climbs but there are two lanes. So can anyone add further experiences and or reasons?

David