When creating/modifying user plan, the conferencing policy is always applied, regardless of conferencing setting in the Plan. So I think if it is a bug or maybe is some other way to disable conferencing features for user and plan?
I checked SCP sources and conferencing policy is always applying (Lync2010/2013 and S4B the same).
Let me explain. The organization conferencing policy is assigned to the BASIC user:
Grant-CsConferencingPolicy -Identity ‘some_user’ -PolicyName ‘organization’ -DomainController ‘dc’
I think that the policy should not be assigned to user if the policy has unticked conferencing feature. Enabling or disabling this feature has no impact in my opinion.