Good point. Total eclipses, however, are very rare, occurring at a given location on the Earth only once every 400 years (or so). Given how small a range any modern uncontacted tribe would be, it's unlikely that anyone but their remote ancestors experienced a total eclipse. And there's a massive, inexplicable difference between a 99% eclipse and a total eclipse. A 99% eclipse briefly makes things darker, a total eclipse changes reality; the visual effects of what you see are disorienting, at best.

So: yes, uncontacted tribes may have seen the sun get briefly dimmer. But even in more "modern" cultures, total eclipses have been cause for hysteria and panic. And maybe that's the best answer to OP's question: take a look at recorded history, e.g. Ephraim Miller and the total eclipse that passed over Texas in 1878.