Security without threat assessment is meaningless because security is about preventing a negative outcome. If the environment is perfectly safe then no security is needed, and if the environment is infinitely hostile then no amount of security will prevent a negative outcome.

Example: Being in an armored car in a war zone is still more risky than riding a bike in a peaceful country side, even if the bike has significant less security than an armored car. The Advice then is not to tell people in war zones to get bikes, nor is it to tell people to get rid of bikes in favor of armored cars. Security needs to match the need, which depends on the threat level.

In my above post I included "targeted attack" as the fourth test, named by security theory as an attack by a motivated party towards a specific resource. If a motivated party wants to attack a specific resource, then the defender needs to raise security above that of general security. Many government agencies have policies based on such threats, and neither a default Windows 10 or default Linux distribution would qualify for such environment. SELinux however was designed for that threat level and is thus common in military organizations, banks, and similar high risk environments.