The vocabulary of the means–ends hierarchy doubles back on itself in exactly one place, and this is it. At the level of the whole organization, policy is the standing charter — the aims and limits that outlast any single effort. But inside Rumelt's kernel, a strategy also contains a policy: the guiding policy, the chosen approach to one specific problem, sitting between the diagnosis and the actions that follow from it.
It is the same word used at two different levels, and the confusion disappears the moment you ask which one is meant. The organizational policy is slow, foundational, and closer to identity; changing it is something like a re-founding. A guiding policy is scoped to a single challenge and lives only as long as the strategy that contains it. One is the territory the organization must never leave; the other is the route chosen across it this time.
See also: Policy, Strategy, and Tactics.