But if we could relatively reliably differentiate, it seems like a large waste of resources avoid a cheap treatment that reduces the risk of future irrational crime to negligible levels.

Yep. But I don't see significant reason to expect detection systems to outpace tricking systems.

I'm doubtful of the reliability of any data

25 to 87% of inmates report suffering a head injury, compared to 8.5% of the general population. The high variation in reports suggests that the data isn't the best quality / most general, but with the most conservative estimate prevalence is at three times higher.