I was under the impression that there are a few stealth UAVs being operated currently.The Sentinel comes to mind and I think both China and Russia have working prototypes.
The article speaks to the RQ-170, introduced 9 years before the article and is one of your links. The idea is that the Air Force abruptly pulled out of a join effort with the Navy and didn’t seem to have an alternative. What happened? Does the AF have something else that is not public or did the manned aircraft program see UCAV as threat to eliminate?
The RQ-170 is a stealth UAV, but not a UCAV - it's unarmed. The other two aren't US, and so are more 'worrying' than 'reassuring' when it comes to figuring out where the US's stealth UCAVs are.