From what I've noticed when this comes up on the legacy CO, now new UA system is YOU ARE CHECKED in, but BP won't be issued until a passport scan or a agent doing a document check.

The legacy United system on flights from the US to Intl would also do the same, check you in but not issue BP and request a doc check (for those with non US passports especially) - on UA this meant an agent doing the doc check NOT a kiosk - so this is a big benefit. However Intl to US would fail to check in entirely if you didn't have a US passport and weren't visiting on ETSA (e.g. are a US resident) - I got hosed many a time on getting on the DM early for at departure upgrades because I couldn't check in till I got to the airport. Continental on BOTH these scenarios checked you in but left it to you to get your BP at a kisok or an agent.

I MUCH prefer this to failing to let me check in at all... I do rather prefer Air Canada's way... They give you a Boarding pass but label it CLEARLY on the top "Document check required by agent" - They will do this if you check in bags or if no bags they call you at the gate prior to boarding. Don't know why new UA can't just do this. ESPECIALLY if you are an Elite.