China heavily restricts the transfer of money out of China, and has been tightening those restrictions over the last few years. $50,000 a year per individual transferring money out of China is the legal limit (yes, the limit is set in US currency). The limit is per individual, so a family can send more.
That screenshot lists a suspiciously exact $1,000,000. For a moment, let’s assume that is real. If your uncle moved $1,000,000 out of China in one year, then that is a serious crime.
So when he hired the scammer on the promise of getting around that restriction, he was hiring a criminal. This is a major issue for the Chinese middle class, people trying to circumvent the limits on outflows and getting scammed by criminals , ie see this article: https://www.google.com/amp/s/amp.scmp.com/economy/china-economy/article/2167731/desperate-chinese-middle-class-take-big-risks-move-money-and-themselves
I know nothing about restrictions on moving money back into China. Doesn’t mean there aren’t any, but my guess would be, when the scammer says he can’t move it back in, he is either lying and delaying people discovered he stole the money (95% chance), or he is afraid of activity that would draw attention to the fraudulent means by which he moved the money out (5% chance).