... it isn't? What word would you use for a government policy that controls the behavior of a private company? The word for that kind of policy is "regulation".
I'm not sure whether there is a widely accepted definition of "policy" that matches yours, but if there is, it's not a helpful one. In general, a policy is a deliberate system of rules or guidelines.
Yes there is, and it is a helpful one. It is good and helpful to have words that just mean a simple thing. The things an administration does are the policy of that administration. That policy been be a deliberate system, or it can be haphazard and arbitrary. It is still their policy either way.