Gotta love how the author is channeling the thoughts of the Mayas.
Well, she does say it is a hypothesis, which means it is her theory of an explanation, not a statement of fact. Significant difference.
There might be other source material factored on but not mentioned. (I don’t think the Mayans kept a written history, but encounters with other peoples might have been preserved in those peoples’ historical tradition.) Or this might be an anthropologist way out in left field.