This new procedure and equipment is partially rolled out at TSA checkpoints across the US, has been for a couple of years now. The agent's computer shows the flight information. No reason to have an extra step to scan a boarding pass since the computer pulls it all up anyways.
To get through TSA as a member of the general public, you have to have a ticket (or a non-traveler gate pass) in your real name (matching your ID, soon to be real ID requirement) for a flight leaving in the next N hours. International flights check your passport at the boarding gate. For domestic, sure, you could swap to another boarding pass purchased under a different name, but what's the threat model there? You've already been screened.
To get through TSA as a member of the general public, you have to have a ticket (or a non-traveler gate pass) in your real name (matching your ID, soon to be real ID requirement) for a flight leaving in the next N hours. International flights check your passport at the boarding gate. For domestic, sure, you could swap to another boarding pass purchased under a different name, but what's the threat model there? You've already been screened.