The USCIS doesn’t make the law, Congress does. Its regulations are interpretations (and workarounds) of the statute. The statute is clear that H1B is a non-immigrant, temporary worker visa. “Dual intent” appears nowhere in the statute. It’s a legal fiction created by the regulation that’s necessary precisely because the statute requires non-immigrant intent. It doesn’t mean that the H1B visa allows either non-immigrant and immigrant intent. It means that you have both at the same time—the immigrant intent from filing for a green card, and the non-immigrant intent required by the H1B visa.

The reason for all this is that the 1952 INA promised the American people that it would not change America’s demographic makeup. Nobody can get the votes to change that in Congress. But the executive branch can change the regulations unilaterally.