Oh it works and it works incredibly well. If they had a personal phone on them they will know who it is in short order.
To the geo fencing, a warrant like this is not that bad. Specific area and time frame. Known crime. They have evidence at the scene. It's one more part of the puzzle they are putting together. They have a crime and they are searching for a person.
Contrast that with Jan 6. They geo fenced a large gathering, collected everyone's info, then pieced through it for people in search of a crime. I don't like that one bit and it will likely end up in SCOTUS. It's very close to a general warrant, if it's not a de facto general warrant. Those are not legal.