Huge game of chicken. Nobody wants to be the one who slew the Obamacare monster.
The IRS was too busy scanning requests to be a 5033C or C4 non taxable entity to be bothered looking for returns which looked false on just cursory review.
The IRS USED to have a screening program at each service center wherein live people looked at the returns visually which came in looking for OBVIOUS multiple filers and the like. How could they have missed something like this with todays use of optical scanners and the like not available in the 70s? To me that means one thing, they were TOLD to look elsewhere and not bother potential illegals. Probably begun under Bush the Jerk.