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.
Say you've done a crime that will be discovered in a few days. You buy a ticket to Detroit and next week the fbi will be wasting its time looking for you in Michigan and trying to convince Canada to search for you in Ontario.
In reality you hopped on a flight to El Paso under a fake name and you are deep into Mexico by now.
Wouldn’t it be pretty obvious you never actually boarded your flight to Detroit? They scan your ticket when you board.
Though totally agree you could fly on a different flight under a fake name assuming that the airlines don’t sync up their records with the IDs the TSA scans at the checkpoints.
I suspect there’s other less visible signals that would make this harder. For example your flight under a fake name might be flagged for being an unknown name/person. Also if you’re on the run it’s hard to buy a flight under a fake name anonymously without a paper trail back to yourself.
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.