Originally Posted by
mgcsinc
Re IAD: So far as I understand it, a random denial looks just like a non-PreCheck companion. Both lack the magic 3 and the logo. There are no conformed reports of true denials despite having the magic 3 / logo. Put more simply, if there's a lane for "random denials," anyone can use it by pretending to be a random denial, including companions.
Except you can only get to that "denied" line, after being rejected by the scanner. A gate-keep prevents non-precheck ticket holders from entering the line before it splits into the two types.
Another observation, and this might be for a separate thread.
The screeners are not "TSA" and are there only to enforce compliance or direct people to the correct line. If you get pass them because they allowed you in the line, for whatever reasons, such as the OP's father going through with him in the PreCheck line. you are good to go (in the line) for security processing.
When you reach the TSA checkpoint, where they check your id and BP, and if precheck, the three-beep alert, that is their only role and responsibility, They don't care if you have GS, IK, premier, or precheck, They just perform their reponsibility, which is to ensure your ID and BP is consistent. If a precheck line, since you don't have a precheck, they just route you to the "denied" line. They don't care how you got in the line or the status printed on the BP (if premier line). Period.
So my guess, if in a separate PreCheck Area, >90 percent of the time, you accompany traveler companion will be denied entry into the line, and on some rare occasions, the screener might let you through, because they don't know the rules.