You're saying that Apple can't find people from less-developed countries with these specific credentials and then offer them a starting salary that's $100k under what they would have needed to offer to someone from California?
> because they are for all legal purposes, an equal to any American once they have EB2.
Equal to an American in legal rights perhaps, but there is no right to competitive pay.
The theoretical factor that's supposed to depress pay for workers on non-immigrant visas is that they don't have easy job mobility - the bar to hire an H-1B is much higher than to hire a US native worker. Once you have an EB-2 (an immigrant visa, that entitles you to a Green Card), that no longer applies - modulo national-security type positions that require citizenship you're just as hirable as a US native.
There’s more to it than that, but that’s one of the big ones. Have you worked with foreign contractors/outsourcing before? If so you know why jumping to another job would be difficult.