Secret police would probably have an interest in lists of people downloading an app tracking their movements no? Particularly if it was downloaded to a mobile tracking device they carry with themselves at most times.

They could argue that attempting to track ICE is illegal, and all those using the app are to be arrested and tried for their crimes.

Maybe they're looking for pretense for more authoritarian action on digital services/internet. We already have a bill in process that opens the door for government censorship of the internet right? They could be priming the public to be ok with them stepping in to shut apps/sites down.