Now how would a chinese model company have the info to produce one of these ?
Honestly? Google! Pictures, dodgy line drawings,.... Just like everybody else. When someone (I think it was Revell) wanted to take a measuring tape to a Raptor for a new kit, they were politely, but assuredly turned down.
Where else would a Chinese company get their info from? From the government's hackers? Seriously, why would the government risk disclosing that they have in fact gained access to JSF programme data for something as insignificant as a plastic toy plane? A lot of (some say most) Chinese manufacturers don't seem to care all that much about measurements on aircraft they would have the possibility to take a tape measure to, why should they be any more concerned about the measurements of a plane that's not even in front-line service yet?