No it can't. Twins certainly do differ in intelligence, personality, income, level of education, patent count, adult SES, or pretty much everything which could plausibly be lumped into a term like 'giftedness'.
> Given that it is impossible to measure heritability directly, various estimation methods are the best that can be done.
??? Is it possible to measure anything 'directly', under your redefinitions of words?
> Applying those methods to geographic features will uniformly indicate that they are heritable.
They would indicate that there are between-family genetic differences, certainly. They would not indicate that they are heritable and it would be wrong or misleading to criticize heritabilities drawn from twin studies on this basis of gene-environment correlation. You can't simply lump together every kind of genetic pattern under your redefinition of the term 'heritability'.
This article is a reasonable summary of the issues with heritability:
https://academic.oup.com/ije/article-pdf/35/3/525/2195546/dy...
The tl;dr is that the people who trot out additive models of heritability as evidence of anything in particular are by and large those invested in the notion of genetic determinism.
Given that it is impossible to measure heritability directly, various estimation methods are the best that can be done. You can estimate the heritability of any trait, with or without twins. Applying those methods to geographic features will uniformly indicate that they are heritable.