No some of them have. It doesn't matter though if none or all of them had been you can still say with confidence that Japan and Denmark have differences in height that given their countries both having first world living standards and an abundance of high quality food nearly certainly means that difference is genetic.

In other words finding the specific genes are less important than say twin studies which can tell you all sorts of important things about heritability and the impact of nature vs nurture despite not telling you anything specific about genes at the molecular level.

Are you understanding what I'm trying to point out?