So, in effect there is nothing hidden from other employees or the employee being hired.
That's not particularly helpful - the only people who see it have an economic incentive to not rock the boat.
The thing to remember about H1B visas is that there are tons of exceptions to the "slave labor" situation. No one sensible believes that every single H1B visa holder is a pawn to keep US wages below fair-market pricing. The problem is that a large number, probably a majority, of them are. Anecdotal contradictions don't disprove the thesis.