Are you referring to this press conference?
I don't think he explicitly mentioned that J-20 is designed for air superiority in that interview. What he did state are that the J-20 has excellent agility and handling characteristics on par with those of the J-10 and that the J-20 employs a side controller stick so that the pilot could operate better under high-G conditions. What he said contradicts the western assumption that the J-20 is incapable of close-range knife fights due to its length, mass, and/or underpowered engines.
Yankee revealed that although there isn't a gun on J-20, there is a location reserved for it. The current assumption is that the weight penalty (half metric ton) is not worth it considering the fact that interim engines are still in use.