Well that's a lot more than we know about the J-20 so far, and in either case, I'm anxious to see that test and evaluation squadron begin to get their aircraft.. I wish we knew about about the fixes for the structural issues, that is always one of the most interesting aspects of any airframe to me, not only where and how the crack, but what the fixes really are when they get these issues resolved!
Yes and no.
The problem is the Russians keep putting information out. It is unclear if it is accurate or not. RT said the contract was signed. TASS just stated it was not. Which is correct? Neither is exactly a very independent news organization after all. Likewise, the Russians are starting the SU-57 is a stealthy aircraft, yet the workmanship has not been great compared to other stealth birds (US or China) and now its sporting an external pod targeting pod? uh. That's...odd.
As for the J-20, there's enormous amounts unknown, sure. However, the Chinese have not been off making galactic level claims. They had stated the J-20 has gone IOC. I wish I could find the source, but I had read there had been a total of 18 production aircraft delivered so far this year (as of June or July). That does not, supposedly, include the ones the Chinese built prior to January 2018. Supposedly.
We might 'know' less about the J-20, IMO, but what we know typically is more accurate. We know far more about the SU-57, but a lot of what we 'know' is dubious at best.