Here Ayi and Xi Yazhou talking about the post-apocalyptic aspect:That’s certainly one possible application of this, but that does not mean it’s the only or even the primary application.
For this to be applicable in a post-apocalyptic world, you will need to have a significant quantity of these container modules already built and in secure, survivable storage to have any to haul out to build a scratch navy with.
But if China already has these built and in storage, there is nothing stopping them from taking them out for use now or in the near future, or to just massively ramp up production for current day usage.
Armed merchants don’t need to be able to go toe-to-toe with opfor naval warships to be useful, especially in China’s case where it has a massive and powerful standard navy. The armed merchants could easily act as arsenal ships and extended magazines for the PLAN’s existing fleets. The self defence capabilities are just to make sure they can deal with the odd leaker and can take care of themselves somewhat to not become a liability which would require significant PLAN assets to babysit and safeguard when in use.
As you pointed out and they also spoke about in this video, as elements from this project becomes reality such as the EMCAT trucks, the post-apocalyptic origins of the project is becoming de-emphasised while people figure out more mundane uses for things that this project comes up with.