Because it’s always the case with the US military equipment capabilities that full capability is never disclosed. What possible reason would the military have in divulging actual specs?

Military: We can penetrate up to 200 feet with this new bunker buster bomb that we spent a billion dollars on…specifically for this site and some sites in North Korea.

Enemy: Build the bunker at 300 feet, I hear their best bunker buster is only effective to 200 feet.

Military: Damn, foiled again!