Bogus. Your next flight can be on Southwest (which, by the way, is not *G) if you are a United *G flyer. It doesn't matter for a United *G traveler what the next flight is (or if you even have one at all). The rule is a "same-day BP for a *G international flight". The situation you describe (the *A domestic flight) would be needed for a non-UA *G flyer to gain access at ORD prior to the domestic segment.