> H1-B is dual intent -
https://en.wikipedia.org/wiki/Dual_intent so there is no winking required.
There is. It doesn't matter in practice, because it's a legal fiction anyway, but here's the legal logic:
For all visa applicants, including H1B, there is a presumption that the person is an immigrant, and they cannot obtain non-immigrant visas until they convince the admission officer of their non-immigrant intent, see section 214(b) of INA. Crucially, you need to argue that you have no intention to abandon your foreign residence. Dual intent have nothing to do with it, this is true for all kinds of visas.
The immigration law says that, as a rule, applying for permanent residency in the US (a green card) constitutes evidence of your intent to abandon foreign residence. Where dual intent policy enters the picture is that the above does not apply to holders of dual intent visas. For them, applying for green card "does not constitute evidence" of their intent to abandon foreign residence: this is the exact language used in section 205b of Immigration Act of 1990, which is the legal basis for "dual intent" policy. Note that they do not say that the rule of abandoning foreign does not apply to dual-intent visa holders, only that applying for green card no longer constitutes evidence of their intent to abandon foreign residence.
Of course, none of it matters in practice, since it's all legal fiction, and in practice things works exactly as you believe they are. The point here is that the practice is based on the legal fiction, on the wink which requires immigration officials to pretend you do not intend to abandon your foreign residence, when everyone knows that this is exactly your goal.