Jia Cheong Tan is anagram for CIA Agent John. If you consider how much went into planning the backdoor operation, it seems virtually certain it's an internal joke.

And why an Asian name? It's certainly exploiting a psychological bias. Apart from what you noted, the names are much more generic than Ugandan names and IMO it's virtually impossible to track a legend down. And the number of OSS contributors from East Asia is much larger than from Africa. Hence a more normalized/frequent occurrence. And lastly if things start going south, some play on the r-card is always up the sleeve of PsyOps personnel.