The jobs being replaced were not able to be filled by local workers.

[Citation needed]

I’d guess that for dev work there is probably a ton of the core devs working locally on big salaries and the h1b workers are being brought on as temps for specific projects

Well, I’m not sure what to tell you except that your guess is wrong. I work alongside h1bs every single day, and they absolutely aren’t temps. That is absolutely not restricted to my company.