Mikhail Pogosyan is not belittling the J-20 as you most think, i have seen most of Russians comments about the J-20, people like Makeinko or Pogyosan only mean this, the J-20 is in the same stage of development of the S-37 or MiG1.44 because they think China lacks the current engine design expertise to really finish the J-20 as a fifth generation.
I do not know but up what i know China has no TVC nozzles on production jets or test aircraft and Russia does, the Su-30MKI are already in production, the same is the AL-41 for the Su-35S. the 117S does allow supercruise, i do not think China at this moment has a supercruising engine on any J-10.
So the J-10B is still uncapable to supercruise as the latest Su-35S.
Russian has even the MiG-29OVT and had the Su-37 with TVC nozzles
if we are honest, China is behind in engine technology and the engine technology is the core of 3S of the 4s for a J-20, supermaneouvrability, supercruise and STOL are engine results, the J-20 only has stealth.
So what Mikhail Pogosyan really means, is the J-20 is still an unfinishied product to impress the West, is not coincidence Gates visit to China was few days before the unveiling of the J-20, nobody can say the Chinese tested the J-20 the same day, that was just a propaganda move.
If China wants to allow people to take pictures of the J-20 is an attempt done deliveratly.
So he means the J-20 is more propaganda than real substance unless they develope some core technologies, and that includes an engine like the new T50 or 117S
but true also the russians are doing propaganda and boasting, so it most be taken with a grain of salt
Except the history of Chinese modern military development tells us that China is very secretive about its projects unless it has something to show for it. The fact that the J-20 was so loosely and easily leaked, especially so verbally by leadership about its intended capabilities, tells us China has a lot of confidence in its capabilities right now. Furthermore, insofar as we know China doesn't do technology demonstrations. I don't think leadership thinks it can afford to, being already behind as it is. Of course, that alone is not proof of anything.
We do know China has TVC technology, even though we've never seen it tested on an airplane. In the early 2000s China demonstrated an axisymmetric version of the WS-10 series.