HAM radio is amateur radio, rules and frequencies are established with the goal of promoting amateur use. Emergency service use would be a professional use and are licensed separately. The statement that citizens are not allowed to encrypt traffic should instead say that HAM radio operators are not allowed to encrypt their communications in accordance with their license.
For those not familiar with it, it is an aptitude test that covers a wide range of topics. The results can be informational. Beware if you score well enough to fill a job in the army that is really understaffed, you will never get the recruiters to stop calling.