If you want to be cynical, here is a good reason. Maybe they are revoking cops "privateer" license for now in order to have a carrot to negotiate with later. Say, in a year the justice dept needs police to "opt in" to some new initiative. They can simply dangle seizures in front of them to get compliance.
Also, the policy allows exceptions. So they could do it on a "case by case" basis, with individual departments and so on. And, if they did change the policy outright, well it hardly requires a press release.
I'm tentatively excited. But I cannot see anything in it for anyone with power. So I just don't see how this would become law.