I suspect that kokonutz was describing the UA midfield terminal (MF) setup while you were describing the international arrivals (IAB) setup for other passengers.
The UA process would involve passengers with onward connections being processed at UA's MF facility while O&D passengers would head into IAB (via moon buggy) and be processed there. For other carriers, it is generally all passengers at IAB.
Nonetheless, unless CBP is screening 100% of arriving passengers, these "mini-secondaries" are random and this particular chokepoint was the GE line at IAB. Perhaps 30 minutes later, the chokepoint is connections at MF.
Last edited by Often1; Nov 18, 2018 at 10:21 am