As a veteran of Silly Valley, I can attest that what you see here is 100% true: job descriptions that are made to meet the legal requirements that “no H1B visa or green card holder takes a job from an American” are carefully crafted to make sure that no one will be able to meet the requirements of the H1B visa holder that has retained the lawyers in pursuit of a green card.
The other dirty little secret out there is this: H1B visa employees are the closest thing to indentured servants since the end of the Civil War. When you’re working under a H1B visa, you have to pretty much take whatever crap your “sponsoring company” is handing out until such time as you get your green card, which requires forking over quite a tidy sum to a law firm like Cohen & Grigsby. H1B visa holders, if fired, by law have to return to their home country before applying for another H1B (or other) visa to enter the US.
This ends up working as a lengthy probation period. If the H1B holder doesn’t work out for the hiring company, they just choose to not continue his employment at the end of his visa; legally, he is now up a creek. If the employer deems him worthy of retention, the employer might hire the lawyers to get the green card process moving right along. At the point that the employee gains his green card, then his pay often goes up, or generous stock options are granted to implement a golden handcuff to keep the guy in place.
Sounds like a sweet deal for the employers. Nice!