The guy quoted at the end seems to think it's the passcode itself that would be incriminating, rather than the contents of the phone. Weird. I've seen a theory that compelling someone to disclose a password can be incriminating because it is the same as asking them to admit that they stored the data in the first place, and obviously there's a case to be made that compelling disclosure of the data on the phone could be self incriminating, but the idea that the password would be something like yesiinsidertraded4 is new to me.

Edit: I missed the part where he's a former federal prosecutor. Mystery solved.