Originally Posted by
xliioper
Perhaps it's implied, but technically, they are not exclusive. While unsaid, they could potentially give your seat away if a) you do not meet the gate arrival time, or b) you don't meet the boarding time. It's not really clear if gate arrival times are only recommended or required. Generally if it's only a recommendation, they will state that.
There’s no requirement to answer to a GA calling your name, so I don’t understand what authority they have to offload you before the 15m mark - which IS a requirement to be on board.