You have 2 countries, C1 and C2.
Scenario 1: C1 has enough demand for 100 tech jobs. C1 only has 50 qualified natives for 100 tech jobs.
The wages of C1 go up because there is more demand than supply.
Scenario 2: C1 has enough demand for 100 tech jobs. C1 only has 50 qualified natives for 100 tech jobs.
Now you put in a H1-B visa program that will pay the same as the prevalent wage as a local native. C2 has enough candidates to fill the other 50 positions.
The wages of C1 will NOT go up because now supply matches demand.
Is Scenario 2 fair? Who gets to decide what fair is? Given the above system, I think I would argue that H1-B visa programs cause wage deflation in C1, even if it is filling jobs that would not be filled and even if the jobs paid the exact same as someone working in the native country.
I am not dogmatic about that though. Willing to hear a counterpoint to scenario 2.