If the person clearly says that they don’t want to change, you must respect their wish. At the same time, one should try to switch to a more viable option in the conversation. Such an approach shows that the interviewer has heard and understood the person's decision not to change and that the interviewer will not go on in discussing of the reasons.
To plant a seed means in this case that the leader emphasizes that the person is welcome to move forward if it becomes necessary.
The person you talk to: No, I do not want to do this. I have other things to think about.
You: So right now taking this step doesn’t fit you. I want you to think about this for a while. What would be appropriate for you to do right now? You are welcome back if you’d like to, in the future.
Note that the interviewer does not choose to reflect the person's resistance, which probably would have only strengthened it. The interviewer makes rather a reflection that is change-oriented and open for further dialogue about a change in the future, when the situation may be different for the person. This is called the MI "to sow a seed for change". In the current situation the person is not ready, but might become that later.
How have you reacted when people did not want to change? Have you tried to persuade them? Take a few minutes and reflect on how you have acted previously, and if you could have done something different in order to plant a seed.