What he actually meant was that the yellow J20A in the first picture was equipped with the WS15.The primer one... Finally a semi-official vague unveiling of the WS-15 huh?
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'Confirmed' by Monkey!
Edit: supplementary material of Oneninety's comment under his own post about the same photos.
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After carefully comparing the details of the pictures, I also believe that the silver-gray painted J20A might still be using the WS10C2 engine.
Meanwhile, the engine nozzle of the yellow J20A in the first picture appears to be longer, which indeed closely resembles the characteristics of the WS15.






