Not exactly. A company only has to advertise these jobs if they are determined to be "H1-B dependent" (> 15% of employees are on that visa), or they need labor

Not exactly. A company only has to advertise these jobs if they are determined to be "H1-B dependent" (> 15% of employees are on that visa), or they need labor certification for a different form of visa (H2-B, E3).