Of course you assume that; if you're talking about what a policy should be, then you work in a hypothetical world where the policy can be chosen. You don't say "but what about some other minor detail! That would require an additional policy choice, and we can't change related policies."

Like if I think my business should open an hour earlier, and you say "but the employees won't be there yet so who will open the doors!" obviously the solution is to also change the work schedule. When you have closely related policies, generally the same person/people are empowered to make both changes.