You're correct Trev - I used to trade in and out of China before they had even been accepted in to the WTO as did many others.
2005 they joined.
I used to buy from 2 factories in Laos back in 2000. They had 0% duty as a favoured nation. They didn't even join WTO until 2014.
So it is quite simple - you have something I want to buy. Can we agree on a price and do the deal?