But once we know that both genes and environment play an important role

How is that not self-evident given the edge cases (puppies going to human schools / children growing up in a sensory-deprivation tank, both not doing well on IQ tests)? Regarding the significant figures, we need to keep in mind those are to be interpreted as "this is how much of the variance factor X explains given a certain scenario". They will vary across e.g. nations:

In a homogeneous environment (e.g. classless society, higher Gini-index), genes will acount for more of the variance than in a mixed environment with people of the same genetic makeup. IOW, as you e.g. change the school system, or who marries whom, so you change those relative weights of nature v. nurture.

You might say "well, given typical circumstances and typical gene pool variances", but consider that the discussion is in any case comparing e.g. the US to sub-saharan Africa (or whereever), which absolutely cannot have the same relative weights for their respective nature versus nurture, unless the different gene variances in tribal societies and the different "school" environment somehow equalled out, a dubious proposition.