The interviews are brutal. But they don't consistently identify talent. I know a lot of people at all of them and turn down interviews nearly constantly (Apple is the only one I've considered - the rest violate my ethical standards. And I'm not going to commute to Cupertino).
For USCIS, it doesn't matter where you work, visa is for the individual and they have to prove their merit against the required guidelines, even an unemployed person from anywhere in the world can apply by themselves if they can prove their merit as per the requirements. That is the beauty of this visa :)
Sincerely, one of the 100k+ FAANG engineers in the world.