Once an employee gets hired (whether it is as a regular employee or a temporary employee through an employment service), the company strongly encourages their new employees to begin interviewing around the company to make sure they are in the best job for them. They do this often within their first month of employment.
Nike is sending a very clear message to their employees with this policy. “Don’t be afraid to venture out. We want you to find the perfect job for you, even if it means that you’ll leave the job you just got into.”