Their guess as to when this settlement existed is probably based on the window of opportunity between the empire of the Olmecs, which ended about 400 B.C. (with a hundred years leeway), and overlapping a bit into the Mayan Classical period, which began in earnest about 250 A.D.
This implies that there is something about this site that is distinctly different from either culture. But it also suggests that whoever they were, they were exterminated by the bloodthirsty Mayans.
This brings up the delicious irony of how, for many decades, the more squishy-minded embraced the notion that the Mayans were “children of nature, who lived at peace with their fellow Indians and their environment.”
This fantasy was definitively ended some years ago, when a Mayan mural was discovered in a hidden basement of one of their buildings. It depicted how the Mayans systematically butchered a people they had defeated at war, in the most horrific ways imaginable, spending some six months reveling in torture and utter carnage.
I believe they have devolved into what we now know as "undocumented workers"
I don’t know which decades you are referring to about the squishy-minded thinking the Mayans were such nice guys. When I first became interested in Mayans about 55 years ago, I was struck by their human sacrifices throwing people into the sacred Cenote wells.
The bloodthirsty ways of the Maya have been part of the US school curriculum for at least 45 years, or I should say, had been, it’s possible that such stuff has been cut in recent years to make way for self-esteem classes and macrame’.