There are places where forex is illegal for private individuals but otherwise
Not a silly question at all! The difference is that this control over bitcoin exchanges has to do with what happens within China which the government can control. Chinese law has no standing outside China. Overseas real estate purchases, all they can do is try and stop the flow of Yuan to other currencies. This however is more difficult than shutting down bitcoin exchanges, it would require going over the books of just about every company within China and trying to do so for every subsidiary and shell company setup from China to see which ones own real estate and what the actual purpose and nature of that real estate is. Rather difficult and even if it were done, it comes back to Chinese law has no standing outside China.