This is an undocumented benefit of MileagePlus
It is sad to say but with technology changing and companies cutting costs/quality, we are all beta testers. Just be glad that we are not beta testers for Boeing, AIrbus, Bombardier, Embraer, GE, P&W...
I upgraded to IOS 12 the day before a big trip. I had minor troubles with IOS12 but no problem with the UA App. However, last night US time, it logged me out and lost my Favored future bookings (those I want to keep checking the prices). I also could not cancel award flights. Neither problem has been fixed. I don't think there was an App update since the IOS 12 upgrade.