Several thoughts:
1. The search warrant goes back several days before the crime. Could be because it was early days and they wanted to err on the side of inclusiveness because they didn't know what they were dealing with.
2. The Secret Service guards the President/VP/families and investigates currency crimes. I assume they were there because of the money.
3. JW did not give them his phone, he showed them his phone. Whatever the persuasive powers of LE, if he had given them his phone it would have said so. This is the information going to the judge. It doesn't mean he is involved but it does mean he was not cooperating completely, at least in the first day or two.