My guess the negotiators had somehow the information that the tariffs will soon be declared illegal so would be smart to let the narcisist think he won, I hope I am right and there is still rule of law in USA.
It buys time, the negotiators also have no power to force each country to implement the stuff , or make the agreement some law.
It would make sense to assume illegal tariffs will be declared illegal with 95% of the chance and just buy time and let the nariisit idiot think he won and go ahead and fuck with someone else for now.