I just spent a few minutes reading up on this. The real crux of this article is that they pulled out genetic variants associated with expression levels of ACE2

I just spent a few minutes reading up on this. The real crux of this article is that they pulled out genetic variants associated with expression levels of ACE2 (from gtex, which should be solid enough). These variants are more prevalent in east asian populations. There's a paper they reference too saying that there's a subset of cells that express ACE2 in the lungs, which doesn't really support expression levels being changed, but could point to the cell system that could be used to investigate this. Nothing really solid yet about dose dependence of ACE2 on SARS-CoV-2 susceptibility. Interesting though!