I don't know about wrong or not but it's a different example from the ones I had in mind.

Take a Manager table and a Department table (obviously manager may not be the same thing as employee - not all employees are managers). Now enforce the rule that each department has one manager and each manager has one department.

This is a special case of a 1-N relationship where N=1. In general most 1-N relationships are not easily supported in SQL unless N is allowed to be zero. That's because SQL FOREIGN KEY constraints are always optional on the referencing side of the relationship, ie the "parent" row must exist but a referencing row does not have to exist.