Ahem...
anyway...
It all boils down to how self-important the authorities think they are.
In the Philippines, you can technically apply for the clearance from abroad but you need to go to the local embassy, have a lone officer (call ahead to make sure he came in for work) assist you in putting your fingerprints on the form that you need to send to your friend/relative back in the country who will personally go to the main office, queue for several hours (there's a quota per day) and armed with your form and an authorization letter to get said clearance for you.
For Singapore, I do remember something being able to do it from abroad.
So if the Chinese want you to fly and appear personally, well....
Take it up with them.