I'm confident that 'drilling' with multiple bombs was the known approach prior to the attack. The planned approach to soviet bunkers was to use repeated accurate strikes of nuclear bombs to achieve a similar drilling for their bunkers.

There appears to be an assumption that the main facility was exposed to blasts from the tunnels and since that appears to be an obvious weakness I'm wondering why the Iranians wouldn't have blast doors between the tunnels and the facility as a form or redundancy. I am still worried that this is part of an approach to slowly warm Americans up to another war, much easier to sell a limit strike as a success, then 3-6 months later when the Iranians have recovered it'll be even easier to sell another strike or a more involved engagement.