If enough people came from far away for a specific date (winter solstice).

You somehow had to feed them. And they probably came with their prey/cattle (that's why some meat came from far away).

I lean less toward some spiritual "barbecue" and more toward contingency. Which means, a lot lot of people came to the site..In itself the idea of mass pilgrimage for the solstice seems more appealing than offering and barbecue.

And at least pilgrimage on a place at a date, is still a current religious occurrence today (mecca) or yesterday (sainte marie de la mer )

While barbecue and meat offering are frowned upon (humans don't like to waste nutriment). But hey! the guy a researcher, so if he want to focus on barbecue ...