> Evading in-person meetings or requests for drug tests Why would they evade drug tests and meeting in person? Do the "techies" claim they are not Korean at all? Surely, a North Korean would pass as a South Korean to (at least) any non-Korean colleague?
Pure speculation, but there is a large North Korean methamphetamine trade. Allegedly, per escapees, many North Koreans use meth for purposes of work enhancing stimulants and hunger suppression. Perhaps these slaves are being doped up to focus on the work?
It's common all among the working class in Asia and the Asian Diaspora (Bayswater Basic if you've ever been to London). It's dirt cheap and keeps you awake while. doing any monotonous or manual labor.
In this specific case, a drug test for a remote job requires ID verification. It's a simple redundancy to verify that the person you hired is that same person.