Yes, the doubling would raise averages, except ... the employer could still fill a “Jr xxxx” position with an experienced H1B worker and then require they do “Sr” level work. So instead of a job that is really a $150K position if an American with ten years experience had it, they claim they only need a junior level person at $60K and bring in the ten year H1B worker at $60K to do that $150K job. Unless they complain about being required to do work above their pay grade, how would the government know ?
Beyond that, we are talking about less than 100K H1B workers, so they are not going to affect the averages very much in industries with millions workers.
Well I can say where I was, most of the IT was H1B or offshore.