Hi Alexey - What you say is accurate. While the Lead Link can set the priorities for the circle, it is the role filler who decides how to allocate their time. Here are a few things the Lead Link could do in such a situation:
1) Ask what projects/actions the person is prioritizing higher than the project/action that the Lead Link is interested in. (4.1.1b)
2) Provide feedback to the role filler if the Lead Link thinks they are working on something of lower priority.
3) If necessary, remove the person from the role.
Hope that helps.