It's not just the new United that is doing this with no email or phone call notification. I had this happen a few years ago on PMUA. My husband and I were flying CDG-ORD-BOS which would get my husband to 2P by a few miles and was cheaper than CDG-IAD-BOS. We showed up at CDG only to find ourselves rerouted via IAD and told that it was a "much better connection." Well, at least that part was true, but what if we had been traveling with someone else or meeting someone at ORD... Anyway, I stopped complaining once I realized that we were now in C. For some reason the agent failed to mention that and I realized it while in line for security. It all worked out well because we got the free upgrade to C as well as 1.5x EQM because we were rebooked as Y.