I'm no expert but I've worked with people who've accessed our corporate VPN while abroad in another global north country and that raised alarm bells. Surely Amazon is at least as careful as my rinkydink org, and would've blocked a request from DPRK, no?
Just speculating since the article's light on details but I'll bet they had to VPN to get on Amazon's net in the first place, and that's where the latency was introduced. Not sure how you'd work backwards to DPRK from there but again I'm not an expert.