Well it's not been a year since the first flight yet, and most prototype aircraft only have a second flying test article sometime in the second year.
The way CAC does it is that they have their second test airframe under go static tests (no flying) and their third one (second flying prototype) is usually equipped with most/full avionics. But we've all heard rumours about how there was a second "2001" J-20 prototype.
So basically the fact there is only one flying prototype at the moment is not odd, and they will have more as the years go on. But I would not be surprised to learn if there is another flying prototype trialling from a desert air field.
