I wish I could be that confident about things that I don't have inside information about! Working against that theory is consistency of the reports, the physiological evidence, and the high likelihood that the affected would be high value espionage targets.
There isn't actually any physiological evidence in the China case. mTBI can only be diagnosed by symptoms; there are no biomarkers for diagnosing it.
The media reports say the symptoms were "subtle and vague, but abnormal, sensations of sound and pressure" that lasted a year. That sounds entirely consistent with a psychiatric explanation.
People working in embassies aren't somehow immune to psychiatric issues (and may in fact be more likely to experience things like this, due to the pressures of their work).
