I pointed out the San are a rare exception. You were trying to make a general case from this. The other ethnographies and historical accounts show high meat consumption. I also suspect the san you are talking about are stunted and trying to get by on marginal land without much game, and so not a good sample.

It bears repeating the simple fact that most places don't have wild plant food for most of the year. Pick up the army survival manual. It's mostly about how to fish and trap in many different ecosystems, because, as it explains, there isn't much wild plant food out there most of the time.