the lost bars are being distributed evenly to all phones so the first bar can be bigger. this way, when you're down to one bar, it doesn't look so bad because that 1 bar is bigger and more muscular that it ever used to be.
At work, at my desk, at a window, 13th floor, downtown, looking right at an AT&T equipment building, 3 blocks away, with huge antenna array on the roof.
Went from always 5 bars, yesterday to 3/4 bars this morning. Interesting.
I have gone from consistently 5 to consistently 1 bar in my room. It sounds to me like my actual signal is 3 bars: Before the update an overestimation of +2 bars and after the update an underestimation of -2 bars.......??