One issue I have with statements like "~50% of the variation is heritable and ~50% is due to non-shared environment" is that they assume the two kind of factors are unrelated, and you can do an arithmetic average between the two.

But very often, the effects are not unrelated, and it works more like a geometric average. In many ways it's more than genetic gives you a potential, an ease to learn/train yourself, but then it depends of your environment if you actually develop that potential or not. Someone with a very high "genetic IQ" but who is underfed and kept isolated and not even taught to read will likely not be a very bright adult, it'll not be "(genes + environment)/2" pour more "(genes * environment)".

Other times, it's more like the environment can help compensate for the genes, offsetting a disability, in a way that you end with "min(genes, environment)" rather than average.

The truth is that the interaction between genes and environment is much more complicated than a mere pondered arithmetic average, and this is rarely considered extensively when people speak of "how much is it genetic, how is it environmental".