[cltby]

But these controls could be done for any IQ-related study. Is IQ-skepticism based on the belief that IQ researchers generally don't use controls? That lead-IQ researchers alone do this?

[astrange]

You can't demonstrate causation by controlling for things, because of collider bias.

https://en.wikipedia.org/wiki/Bad_control

You need better methods like an intervention study or a natural experiment to show causation.