but what does this say about mainstream understanding of econs if bartering wasn't a thing?

Yeah, that is the 900 lb question Kevin. David Graeber goes much more in depth in Debt: the first 5000 years , and is an absolutely fascinating book. I think it says that there may be some very basic ideas about our reality that are worth extricating from our minds and taking a closer look at.

I'd assume that barter begins from agricultural perishables

Which makes sense from our perspective. From Tribal Peoples' Perspectives (the ones we know about anyway), it appears that their actual behavior is very different. The tzutujil maya in the Guatemalan Highlands for instance, hunters are not allowed to eat their own meat, and many of them are practically vegetarian. Any animals they manage to bring back get distributed to young women and their grandmothers of other families who cook them, process or dry them, and distribute the food back through the village (Lake Atitlan, their "village" was about 40,000 people in the 80s before rampant genocide and cultural violence ensued from radical industrialized local christians with modern weaponry).

The families of the hunters had to eat meat that was caught by a different hunter, and processed by someone else. They're not allowed to eat their own proceeds. No formal exchange happens, it's just part of peoples ritual in this context. Consequently members of farming families are largely responsible for feeding the hunting families.

It seems that the way people live together all around the world has been incredibly diverse, we can only begin to understand the magnitude of differences in how every group of humans sees their world and works within it. It doesn't make it any simpler to imagine what that means for us...but I find it somewhat inspiring that the possibilities may be wider then we thought.