I can't find any real details, but from what little reporting there is this sounds like the same area of research they were using to play games of mario when I was in undergrad. Growing neurons to do computational tasks is to the point that it's in the realm of experiments done by youtubers. The pervasive problem is that these structures can't survive terribly long; they lack the rest of the biological systems like a circulatory or immune system that a human brain relies on, and so die off extremely quickly. Growing large numbers of them also doesn't do much, as without some genetic structures which we barely understand (as in, we don't know if they for sure exist let alone what they look like) the development of the neuronal network is invariably destructively adversarial.
Given the other reporting on this topic touting this development as a new weapon in the war with the US, I'd suggest being very skeptical (and not worrying about the ethical implications) until they publish more results.