Yixing's situation is complicated. The THAAD issue hasn't really gone away and there is still tension between the two countries. No other Chinese idol in a K-Pop group is in the same position as him so a comparison can't be made. No other idol is as popular and well known in China as Yixing and no one else has been appointed an ambassador by the government like him. He and SM have to be cautious with his schedule. They don't want to piss off his Chinese base or the Chinese government because that could be career ending. I think they are testing the waters with this comeback. I think they are looking to see what the reaction will be to it (from certain parties already mentioned). I mean, he was in Korea all summer. There's no way that he only recorded one of the versions of the title track in that time.

He's only on the chinese version.