Obviously racial effects go under this category as well.

I think you meant "obviously racial effects could go under this category as well." It's not the case that we live in a society where only members of particular races are allowed to work at all, and that this forces a correlation.

It covers anything visible. So a high heritability is compatible with genetics being a cause of competence, and/or prejudice against visible genetic characteristics being important ("Our results indicate that we either live in a meritocracy or a hive of prejudice!").

There's a natural experiment that can distinguish between the "colorism" theory and the "heritability" theory. Can you think of what it could be?

(I'll link it in about ~5 hours.)

But is it possible that IQ itself is in part a positional good?

The easiest way we can look at this sort of thing is comparing individual returns to IQ on income and national returns to IQ on income. If IQ is used mostly for absolute improvements, the latter will be larger than the former; if it is used mostly for predatory purposes, the former will be larger than the latter.

(Hive Mind is the recent book that details the data. As I recall, the latter is about twice the size of the former, i.e. IQ does actually cause absolute improvements in wealth)