The reason why they were willing to try is probably because of the over 80% successful rate of Xiao’s surgery in China.
If the successful rate is a misrepresentation; and if those patients have the some the problems as that of their Chinese counterparts, they can sue Dr. Xiao, no matter what agreement they signed with Xiao’s team before the trial.
If Xiao is sued by those patients, all the foreign doctors who support Xiao, including the “31,” will shut up.