This thread is about a unanimous ruling from the USSC which we can all agree is (regardless of their leanings) a bench of scholars (especially their clerks btw who are the pick of the country's best).I really doubt any of your scholars are going to easily explain away why the state can't crack open someone's cell phone without a warrant but can nonetheless rifle through (at minimum) the metadata off that cell phone.
You're comparing 2 things that happen a distance apart.
Local police, during a stop, can't pore through your cellphone. At the same time, the NSA can go through your metadata and more if they're investigating you for terrorism. Those 2 things occur separately. It's not as though Officers Toody and Muldoon get on the phone with Chloe O'Brien during the traffic stop and ask her what she's got while they're administering a field sobriety test.