Hmm, you're right, it seems like the T6/7 FIS doesn't stay open until the last UA international arrival of the day. UA1277 parks at T7 but presumably pax are bused to TBIT. I suspect this is the case because UA's flight status shows carousel 7 for bag claim, which doesn't exist at the T6/7 FIS (they're lettered A/B/C there).