Though, not that I doubt them but I wonder where they get their sources. Unlike the Guancha trio who actually has insider sources, SOYO to my knowledge is basically just a really dedicated guy with decent past record who digs through papers and possibly some info from followers etc. I'm not really sure who Oneninety is but someone apparently said he works at CAC, though given how proper projects are likely highly compartmentalised hence even if CAC is contracted to build parts for this new aircraft, I doubt the average employee would know anything about its purpose assuming he even works directly with production, administration and other non technical staff would likely know even less.
Information diffusion is quite interesting and it is a key part of what we are doing. The fundamental principle is that information exists and it spreads, just at different rates and through different avenues.
SOYO is apparently some kind of teaching assistant at a university right now (something of this nature, I don't exactly remember). He might just know someone, maybe a former classmate who works somewhere relevant, or someone he met at the Zhuhai Airshow and stayed in contact with. Alternatively, he might know where to look in places that others do not.
These people also all have their private groupchats.
Another factor to consider is the denominator. We should expect there to be many projects currently being undertaken, projects we don't know about. At some point, statistically we should hear about something.
In fact, I have noticed that the Guancha Gang has significantly reduced how much information they disclose over the past two thirds of the year. It is highly likely that they thought they were attracting too much attention. I did translate entire sections of what they said, and others have done similar things as well. One post even ended up being shared by Deino on Twitter and going somewhat viral. I imagine they did not like that and cut back on what they disclose. Having this kind of information spread on the foreign internet and traced back to them is very sensitive and potentially dangerous, so they need to be extremely cautious.
Which means I think the PLA watching "unknown unknowns" set is currently larger than what we observe.