Vietnam could have had those nuclear reactors already operational by now but they stopped the project over a decade ago. Now they want to restart it.
It won't be ready by 2031 when they haven't even cleared the site for construction. Heck, did they even pick a site yet?
Consultations with local authorities have to happen. A site needs to be selected, soil samples need to be taken, the site project needs to be designed. The site needs to be cleared then concrete will be poured to build the base. All of this takes years and only afterwards will nuclear power plant construction start proper.
The US government has also already started blocking dollar transactions for Rosatom. They blocked Rosatom's $2 billion USD payments to contractors at Akkuyu NPP in Turkey slowing down project construction. I.e. they stole $2 billion USD from Rosatom.