No offence, but you're completely misinterpeting the context here. The term "history" in DBH can either refer to a timeline or just the entire multiverse flat-out, depending on context. The "histories" that are shown and stated, floating around inside Mechikabura have been outright stated to be separate spacetime-continuums/timelines. Literally
4 of those "
histories" shown floating around, are the histories where the Dark Dragon Balls landed to and which were flat-out stated to be
separate spacetime-continuums/timelines or
spacetimes. The other is the GT timeline where Xeno Trunks and the others even had to fight their
alternate timeline/history selves.
Simply put, Mechikabura is shown and stated to be absorbing alternate histories/timeline
s. Chronoa states that he's swallowing up all of time and
the world is going to perish, because he's absorbing entire timeline
s. In the end, Chronoa confirms that the world
did perish and history was no more. It's not that hard to understand. The term "history" in the end is simply referring to all of existence, while the term "histories"in the beginning is referring to the numerous timelines being swallowed up, and "the world" is obviously referring to the multiverse as a whole, as he's already consumed various timelines.