Your quote from their link is a boilerplate minimum restriction that applies when no further restriction is provided. Most places, especially "sensitive" ones have even stricter limitations. Go ahead and try and fly a drone 500 ft above a military airbase, you'll meet some fun people and have plenty of free time to pick up a new hobby.

Nuclear silos are generally not that sensitive, because they are all 60 years old and everyone can identify them on satellite imaging, but if you fly a drone near one, you will definitely be surveilled by some security, whether you know it or not.