Yes, this is probably it, they might already have the H1B person lined up, but they've got to offer the job to citizens/permanent residents. They often do this

Yes, this is probably it, they might already have the H1B person lined up, but they've got to offer the job to citizens/permanent residents. They often do this in a way that guarantees that they will get no takers. The immigrant will agree to a low salary because the alternative is getting deported.