I don't know why Danger Room is so surprised about this; apparently one of the Hungarian Air Force's new Saab Gripens managed to claim a shootdown of a Eurofighter Typhoon during an exercise (is that the first encounter between 4th generation fighters?).
The first point is that the Gripen isn't second-rate at all, as DR implies; it's a genuine fourth-generation fighter. The manufacturers (Saab and BAE) respectively built the Saab Viggen, an F15E/Tornado GR1A/Sukhoi 24-class strike aircraft in the 80s, and the Tornado itself; BAE, of course, is also a major workshare partner in the Eurofighter.
The second point is that there is a history of lightweight fighters doing better than expected; back in the 60s, the Singaporean air force's BAC Strikemasters - Jet Provost initial trainers with guns - occasionally shocked the RAF Lightnings and RAAF Mirages. At the same time, the North Vietnamese MiG-17s and -19s did very well against US F-4s. More recently, the Sea Harrier FA2 had a similar reputation. This is actually why the Americans decided to develop the F-16.
It all goes back to John Boyd, and his ideas of the OODA loop and the importance of shifting energy states; if you're small, you'll be seen later, and you can turn tighter without losing as much energy. Of course, smallness has costs; the Gripen is comparable to the Typhoon in many ways, except range.