In India classical music one must go through a long alaap before the actual composition takes off. Similarly I have to put up disclaimers to my Indian compatriots who get upset about things I say about China on this thread.
Here is a disclaimer I have posted several times before on this thread. 
- China is rapidly progressing
- Do not underestimate China
- China is sitting on US$ 1 trillion
- Quantity is quality
- China is manufacturing world class electronics
- You get what you pay for "You wan' cheap. You get cheap"
- Helicopters, Planes, ships and chips may look like copies of Western or Russian stuff, but inside they are all different and far more advanced. The resemblance is purely coincidental.
To these points let me add
1. I have great respect for China
2. India is inferior.
3. I must not act too big
4. They have megaton bombs
5. They are efficient while Indians are corrupt and inefficient
6. Indians are silly to criticize China
Having got that out of the way, I find it odd that Chine seems to be doing to USA what Pakistan did to India for many decades. That is to pretend that all developments in India were only pretence and gloss and that Pakistan was right up there, equal and shoulder to shoulder with India. Pakistan lunched satellites, manufactured tanks and jet aircraft - all better than India and before India.
These two aircraft J 20 and J 31 seem to be a Chinese attempt to put up a similar show. Oh they are pretty and the shapes, even if copied look convincing. But Pakistan's empty rhetoric became evident only after 10 to 20 years. Anyone who plays with aerodynamic shapes will know that a plane shape object, suitably powered (or bestowed kinetic energy) will fly, given some basic lift surfaces and balance.
But there is a huge huge difference between a steatlh fighter shaped object and a stealth fighter. The irony is even more acute when you see that the Chinese have not even bothered to state a function or role for the two aircraft. he Chinese like symbolism. they know that half the world will be awed by these shapes, the other half will laugh at the pretence. But still they do it because I think the Chinese actually like the awe and utilize the critics views to prove to other Chinese that the world is against them and does not want to give them their due even though they are right "up there" with the best. 
Because the world has been ruled by Western nations and the USSR we have become accustomed to a particular style of international behavior. That is why it took so long for people to understand that you can actually get a country like Pakistan that lies through its teeth and negotiates with a gun to its head. 
China too shows this strange combination of behavior where spectacular and praisewrothy things are highlighted with great pride, expecting praise, while failures and dark spots are completely hidden away. The failure to give any explanationor specs fro the J-20 and J-31 are ignored and stonewalled. This is a nation for which honor and respect in public is important. It is a Chinese version of the old Paki/Arab echandee.
Al Chinese displays needs to be filtered through this lens as well to gain insight into why they do what they do. Just my pisko thoughts