You are not a position to comment on credibility of peer-review journal. The outliers are discussed in supplementary material which I quoted above.

That "Slovak" is not an outlier, seeing as they are not a Slovak to begin with. In the Eurogenes or Dodecad project they would have never gotten an SK label because they are way to far from where Slovaks logically should be. If I had to hazard a guess I would assume that individual is a jew from Slovakia. Furthermore it is a very poor sampling technique to not ask what the 4 grandparents of each individual are.

As far as geography goes, look at what they labelled as YG and RS on the European map in the corner of their genetic map. Likewise Yugoslavia was long gone by 2008, which a two second google search can reveal to anyone. I would assume that the editiors and publishers of a peer reviewed journal should possess some basic general knowledge about the geography of the continent that they are studying.