Here is what is so asinine about SSSS and screening at the gate. If someone is thought to be a threat, so that the passenger gets assigned SSSS,and that person is not secondarily screened at the checkpoint, then shouldn't the entire terminal get dumped and re-screened? I hate to even bring up the subject, but let's think through this idiot scenario.

Passenger is assigned SSSS, so somebody or some software concludes passenger is a threat.

Passenger gets through checkpoint screening, and de facto does not alarm WTMD or have anything outlandish in carry-on bags that showed up on X-rays. (Query- if someone crazy shows up on checked luggage, does TSA then inform checkpoint or gate so that additional screening of that passenger occurs?)

Once passenger is through the checkpoint, into the "sterile area", passenger is not explicitly observed. If passenger was able to get some prohibited item through the checkpoint, the passenger could theoretically stash the item for another passenger-terrorist to carry on the airliner.

At the gate, gate agent sees the SSSS and calls for TSA to screen passenger there. Problem is, the SSSS passenger has had the run of "sterile area" for some period of time. "Sterile area" is no longer sterile. If TSA is going to be internally logically consistent, such a breach should result in a terminal dump. Screening the passenger at the gate is purely a cosmetic action to satisfy some meaningless SOP that a bureaucrat developed. Only God knows what SSSS passenger could have hidden in "sterile area" for an accomplice to carry onto airliner. Of course, if checkpoint screening were worth a damn, a passenger could not get anything truly harmful through that step. Either way, this procedure is more Kabuki security, just an entertaining show rather than actual security.