Not necessarily. The French built the metre gauge line all the way to Kunming from Hanoi. Also from Hanoi to Nanning in China. So transshipment happened at these two cities which are a long way from Vietnam. The Chinese are standardizing all their railways. I believe that Nanning has been converted so the Kunming line could be next. Most of it is in China so I expect that the Chinese will pay for that. I think that the article above is about the work to convert the relatively small part of the route that is in Vietnam.
In the old days Kunming did not have any direct connection to the Chinese network but that might have changed. We all know about the Chinese new high speed rail lines (four north-south and four east-west) but I was surprised to learn in talk by the Chinese railway delegation now in Australia that they are also building heavy haul freight lines to many part so of China. So if Kunming does not have a connection yet it soon will.