>smaller impact than expected

Yes, it’s about both effect size and uncertainty. That’s science. But your original post also brought policy into play. Unless you actually know that uncertainty, effect size, and those costs (including opportunity costs), you’re just making stuff up because “it just makes sense so it must be true.” That’s neither good science, nor good policy.

Advocating for big policy changes (like changing building codes) without understanding those aspects is like jumping into a pool headfirst before knowing the depth.