Now that I've seen the Sing Off China clips (which I didn't know existed), I'm wondering about the re-dos. Surely those were because the actual song arrangements were done by people on the US version, and thus they were intellectual property that the franchise could re-use? Thus, it's not REALLY Freemen's fault that they were given the arrangements to do... I'm guessing they weren't alone in that sense.
If they had only stuck to songs sung on The Sing-Off, I might have agreed with you. One of the most egregious group is called ET and they simply copied Pentatonix performances, including songs not sung on The Sing-Off such as Telephone
which young Scott, Mitch and Kirstie sang when they were still in their school choir
and Somebody That I Used To Know
which was done after they had won The Sing-Off
. Its plain simple, they copied.