To be clear, I'm not making accusations about Vietnam, I was just thinking about it and found it a little strange.
I can think of some fairly plausible reasons, but just because those reasons are plausible doesn't mean they're actually correct, so I was wondering if anybody had a more concrete historical and materialist understanding of the situation.
Probably has a lot to do with it. As I understand it, the DPRK also isn't super duper China-friendly, despite Western propaganda depicting them as being best of friends or even the DPRK basically being China's puppet. I wonder if the DPRK's increased relations with Russia will create a similar but different sense of realpolitik balancing between two powers?