IMO Trump knows how damaging tariffs can be to the U.S. consumer and has only used the threat of tariffs to get some concessions out of XI, whatever they may be. Some may say concessions that will benefit Trump, personally. I don't deny that but I think his prime motivation is to catch, for lack of betters words, off guard.
No matter what, XI knows Trump is not bluffing if he doesn't get anything out of it.