Flew an SFO route yesterday, and my BP stated a boarding time of 30 minutes before pushback. Yet, when I got to the gate 35 minutes before pushback, they were already deep into boarding zone 3. I was in F, so I had to withstand the glare of many dozens of passengers by using the PreferredAccess line to cut in front. Some of the people in the regular access line tried to passively aggressively block my path forward at the head of the line (between where the lines merge and the agent). Anyway, I still had to stand in the jetway for about 7 or 8 minutes, and obviously all overhead space in F was full by that point.

Just wondering who makes the call on how early boarding begins. I've flown this route many times, and the boarding commencement time seems wildly inconsistent. I know that every last seat on our A321 yesterday was occupied.