I am objecting to their initial motivation: it being surprising that "small" DNA changes lead us to be vastly superior to Apes.

They suggest in the disappearing ink thought experiment that this is because the genetic change is sufficient for us to pass some critical threshold (allowing cultural transferences of ideas).

That is a completely different from my complaint. I complain that they subtly mischaracterize how we should think about DNA changes. The number of DNA base substitutions is a pretty meaningless metric in the context they are attempting to use it.

I dont disagree with their argument that there can threshhold changes and that cultural accumilation might be one of them.