They only have access if they are in the job, you can keep security clearances for a period of time after a job that required it. The point Q is trying to make us that having a security clearance means the government can legally monitor you for suspicious activity without a warrant.
If you have a top secret clearance and have access to top secret information you don't still have access to it when you leave your job, even though your clearance remains active for some time. The clearance only allows you to get a job that may have access to that type of info, not to have access to it whenever.
People are still not getting it, having a clearance does not make you less detectable it makes you more detectable. The government legally monitors people with security clearances, you automatically allow the government to track you for national security concerns when you obtain a clearance, without a warrant.