Exactly! The companies often prefer the people on H1B visas because the workers have to be much more subservient or risk being deported and they have leverage to pay them at the lower end of the salary range for the position/level.
Interestingly, the meat ag and farming employs (no pun intended) similar tactics with undocumented people working in near-or-de facto slavery conditions that are very dangerous. The major meat processing plants in the US advertise salaries in Mexican and Central American newspapers to encourage migration. And, the US immigration system is a Kafkaesque, Byzantine, understaffed nightmare purposefully to keep official immigration meeting socio-political objectives of appearing selective. In truth, it facilitates megacorps importing large numbers of foreign knowledge workers through official channels while criminalizing and marginalizing undocumented people to be under the thumbs of other megacorps monetizing unpleasant work society inconveniently needs to function.