FlyingHoustonian

They do not know the complete list.

Think about it as others have noted. Passport scans are not required to enter many countries, and many people (such as myself) have multiple passports (I have four, from two different countries and not all are linked) and the government is too inefficient to track them all and the data. And some countries do not stamp US passports regularly upon entry or exit whereas others do electronic scans in system that get shared and verified. PNRs, for the most part, do not list non aviation travel, and POV or other travel is not always linked via the same type of systems air travel uses which get back to CBP.

As I discussed in other threads years ago CBP paid me and others as contractors a few years ago where I got to watch them in action (open source stuff); so from that alone I say trust me, they are as inefficient as they come. Seeing it both from the inside and outside as a user it can be mind boggling. That said it has gotten better over the last 10-12 years. The new GE biometric match is an improvement IMO, for example. As an early, early beta test user of GE since it was just at three US airports, I have seen many changes and not all bring more efficiency, but overall it is still one of the better government programs.

That all said, as others note, defer to caution and list everything even changing planes. Changing planes in IST flags people all the time, for example, so if you do not list Turkey you could be SOL. And yes, as a TRUSTED traveller program, integrity checks are part of the system. Last thing I am is a CBP apologist or cheerleader, but the onus is on the traveller for the forms, and to not make goofy or off-colour comments to the officer in the GE line or what not and complain about the system. There is always MPC or whatnot if one does not want to the more onerous (and not-free) GE checks.