-(으)ㄴ 것 치고(는) sets a low expectation and then reports that the result beat it. That is exactly how every line here works: 치킨인 것 치고 정말 촉촉하다 "really juicy, for chicken," [급하게 간 것 치고는 오래 있었음] "stayed quite a while, for a rushed trip," 패스트푸드인 것 치고 좋다는거야. It can also cut the other way, marking a mismatch: [홍보하러 온 것 치곤] 네가 뭘 홍보할 게 있냐?. Expect it constantly in food reviews and variety captions, where it is the standard way to soften a compliment.