Used this again a week or so ago at SFO T3 PreCheck line. They had signs advertising it. The TSA (CSA) agent initially stated that I only needed my driver license (presumably thinking I had my phone out to show by BP), but once they realized I was using mDL they simply let me scan the QR code, stare at the camera, and I was through in a few seconds.

I watched the screen a little closer this time, and it stated that it was doing something over Bluetooth right before I got the prompt to share my details, so I'm guessing it's BT only and no need for actual internet access.