There's nothing that makes the digital data on a phone any different or more private than the physical data in a filing cabinet in a home or office, both which

There's nothing that makes the digital data on a phone any different or more private than the physical data in a filing cabinet in a home or office, both which require the same level of judicial oversight to obtain (your first point is factually incorrect with regard to this case, as the FBI does have a warrant to search this phone).