As a person who collaborated with Deka Ironworks Simulation (DIS), I am pretty sure DIS over-performed JF-17 deliberately. China's official data (Chengfei) indicates the JF-17 a mediocre turn fighter with a STR of 18 deg/sec (I cannot post it here due to rule 1.16 but if ED contacts me I will show the proof). This number is in line with airshow demo if you use a stop watch to time its 360 turn, which is much longer than that of a Viper. DIS boosted it to 20+deg/sec. One of DIS employees told me that it is done deliberately by reducing trim drag and induced drag.
Also DIS exaggerated the performance of SD-10 to give it UFO-like maneuverability, and refuses to fix it. Enraged by its behavior, ED revoked some access of 3rd party devs and forces using official API for development.