And you're Monty Python's black knight. You didn't answer the question. Have you ever flown a fighter before?
The Rafale is said to have more than 30 deg/s ITR at what speed and altitude? A kite can have a 30 deg/s turn rate at a low speed and altitude. If your interest is in comparing the Rafale with the J-20, do you know what the J-20's ITR is in the same flight conditions? That statement means nothing without context, and that you think it means anything is very telling about your understanding of flight.
Don't bother with this guy. He's an absolute fool and persists with this sort of nonsense. Everything he said is actually either untrue or unproven but he makes it sound like it's already physical law that's engraved in stone. Just say Su-57 > J-20 and he'll go away. For those who want to know or come from a technical background, J-20's very forwardly placed and large canards are to create a greater moment along certain points of rotation behind. It's not much longer than Su-27, and it's definitely a hell of a lot more LO than Su-57. It is designed primarily as a fighter that allows for strike and interception like any multirole air superiority. However, it is clearly not an interceptor. If it were, it would be designed to carry long range missiles internally which it can't.... yet. 15 tonne weight is unspecified and I don't believe for a second it is the total take off weight. It could have been referring to unfueled, unloaded weight or even frame weight... we don't have an idea or do we? Not sure can't understand Mandarin well enough.
Basically article is as trustworthy as official Chinese government, which is not at all reliable. Don't read too much into it. As for B787's comments. This is coming from a guy who believes F-35 was hit by S-200 without even properly investigating those claims. Believes stealth is easily defeatable by Russia with close to zero real evidence but believes Russian articles written by dodgy stupid journalists with a political agenda. Believes Su-57 to be VLO despite completely exposed engines (intake to nozzle is a straight path) and all round rubbish attention to detail and rough surfaces.