He was probably expected to be in the minors for a little while as he was a second tier signing still young (24). The reason you have a rule like the draft in place is to encourage more young players internationally to come over. I know that younger international players get traded all the time, though most have several years in the organization before that happens (who is trading for that 17 year old before they even play in the DSL?).
The goal is to attract more kids to your sport. This is a tiny thing that will potentially make the next kid stay in Asia. Like all the draft rules make the next kid want to play basketball or football.....