From what I can see, those stats do not look manipulated to suit some national interest. It looks indeed that Croats (those taken from that sample anyway) do seem to share more similarities in terms of frequencies with Southern Germans (and for some strange reason, Saamis also) than with other South Slavs, though other internet sites seem to show other frequencies that say otherwise: http://www.eupedia.com/europe/european_y-dna_haplogroups.shtml
I agree that one sometimes sees wishful idiots from Croatia that wish they were anything but Slavic (claiming some pseudo-Gothic theory, for example), but I don't think this study is example of that. Personally though, if I was to give my personal advice to some of those fools who talk of only Gothic, Sarmatian or Illyrian origins, I would remind them that all those peoples no longer exist and only Slavic language, culture and identity remains. Those other three tribes were conquered, dethroned and forgotten, though indeed bloodlines of those assimilated peoples still runs in veins of Croatian folk and this is why it does not surprise me that Croats (as well as Slovenes) seem to share high frequencies of I2b (native Balkan haplogroup, probably found mostly in Illyrians), R1b (typically found in Celtic and Germanic countries, indeed from blend of Gothic and Celtic settlers in Balkan region) as well as R1a (typically found among Balto-Slavic and ancient Scythian and Sarmatian peoples), making them indeed blend of all this peoples, yet fact is that only Slavdom remained when one happens to look at their language, culture and heritage (not so much genetics though).