I have no problems believing China has made great strides and could produce some world-class military systems. But, Project Leaders/Directors putting positive spins on his/her 'baby' is common, and one might say expected. I'd like to hear more about challenges on the project and how the team solved them though.
Well, in my experience, Chinese officials are usually quite realistic when evaluating their own projects.
If you remember, the Chinese officials would say something along the line of "we want to learn as much as we can" in the 1990's.
Then in the 2000's, they began to say something like "we are trying to close the gap". In fact, they still say this a lot.
Then sometimes, someone would say "our stuff is close to world-class", or even "as good as those best in the world".
Then every once in a while, you would hear someone say "our stuff is the best in the world". Not often, but we do hear this kind of talk now.
And Chinese officials who are in charge of the project are usually more conservative about his/her own projects. I think this is mostly out of necessity because they don't want to seen as "bragging". Also keep in mind that Chinese officials are promoted, not elected. Bragging yourself might win you popular votes, but won't look good in the eyes of your superior. In Chinese politics, bragging is a sign of immaturity, not a good virtue to have for promotions.