If the stats showed that most of these guys transitioned after entering the court or prison system, we could conclude most were using it as a means to gain an easier time in prison or other considerations. That tells us something about how far offenders will go, but that's about it.
On the other hand, if they found that there were an unusual number of sex offenders who had identified as trans before that, it would suggest that there is some other link - maybe that people who offend sexually have other kinds of abnormal or unusual sexual proclivities, perhaps, or something else. which would be a significant finding.