Strange and contradictory AGC characteristics in datasheet
From the quotes you show, I would assume that "gap time" is not the time from the AGC pulse to the data start, but instead the gap from end of data stream to next AGC pulse. Think about it: The AGC pulse sets the sensitivity level, and the data should come right after that. If the gap is too big, then the AGC circuitry will have time to recover, and thus the data will not be decoded in context of the initial burst.

The gap time between codes is there both so that the AGC can recover if you move the sender, and so that the decoder can easily sense the difference between successive codes versus a very long pulse train.