This summary is not the rule. The rule text controls.
A junior lawyer still has to follow the rules of professional conduct, even if a boss or supervisor told them what to do. Being told to do something by another lawyer, even a partner or senior attorney, does not excuse a lawyer from breaking ethics rules. Every lawyer is personally responsible for their own conduct.
That said, the rule also protects junior lawyers in gray areas. If there is a genuine question about what the ethics rules require, and a supervising lawyer gives a reasonable answer about how to handle it, the junior lawyer can follow that guidance without getting in trouble. This only applies when the issue is truly debatable, not when the rules are clear and the supervisor is telling the lawyer to break them.
In short, this rule balances two things. It makes sure lawyers cannot hide behind "I was just following orders" when they clearly violate ethics rules. But it also recognizes that newer or lower-ranking lawyers often rely on more experienced attorneys to sort out tricky ethical questions, and they should not be punished for trusting a reasonable judgment call from a supervisor.