How many extra engines would the chinese be getting?
It does not mention that in the article. But in the article “reports have surfaced that at least one of the J-20 prototypes uses a Russian borrowed engine. Access to Russian engine technology may therefore be one of the driving factors behind Beijing’s interest in the Su-35.”
This was also mentioned in the article:
“China’s inability to domestically mass-produce modern high-performance jet engines at a consistently high-quality standard is an enduring Achilles heel of the Chinese military aerospace sector and is likely a headwind that has slowed development and production of the J-15, J-20, and other late-generation tactical aircraft.”