I don't fully understand this blog post, but possibly of interest:

https://theinfinitesimal.substack.com/p/the-missing-heritabi...

In particular, see the third chart, "GREML-WGS heritability estimates," which shows that heritability for height is pretty much the same when they try to adjust for environment in different ways, while the estimates for IQ vary a lot.

Gusev seems convinced that some environmental effect is inflating heritability estimates for IQ that are based on twin studies.