You should read the linked decisions in the article. The FCC learned about the dead air because the stations themselves filed Special Temporary Authority paper

You should read the linked decisions in the article. The FCC learned about the dead air because the stations themselves filed Special Temporary Authority paperwork with the FCC specifying that the station carrier was not active during that time. So, it was not active monitoring, but passive paperwork review, triggered by the license application itself, that caused the ruling. The FCC does not actively monitor stations in any way.