This is really shocking and unique way to tell the hacker about the case I mean why would the hacker give a shit about the case if the court or authorities only know his wallet address then what fear hacker have plus they also spend 100$ + fee too to send a pdf link to the hacker. And there is still a possibility that once the hacker gets caught he would say that he did not see the link in the OP_RETURN.
I mean, this data is not directly shown in some wallet, to see this we have to use explorers. In my opinion, it's a waste of money and resources, they are just finding ways to give some relaxation to the victim who lost $100k that we are doing something.