A part of the story that has always made the claim more plausible to me is the claim that apes tend not to get cavities at the same rate we do. Since they have teeth that are as susceptible to acid as ours the story goes their diet tends to lead to other populations of bacteria in their mouthes out competing the cavity causing ones. Then people will go on to say that this ecosystem of mouth bacteria have co-evolved. The reason we have so much trouble is that we've changed our diets drastically relatively recently aka a few hundred thousand years. It sounds like you would argue that some part of that story is wrong. Maybe the bit where eventually a less damaging microbiome would evolve?
The idea that primates get cavities less frequently than modern humans is a bit outdated and not terribly supported by recent studies. The main difference is in the location of the cavities, not frequency – apes tend to get cavities in their front teeth, humans tend to get cavities in the molars.
