Is platform un-linking functionality for mixer plugins broken?

Question

[Wwise 2016.2.6] 

After unlinking the mixer-input plugin toggle, assigning a new mixer to one platform will appear in the GUI to override another. 

Unlinked mixer references XML

<Reference Name="Mixer" PluginName="Oculus Spatializer" CompanyID="266" PluginID="146" PluginType="6">

<ObjectRef Name="Oculus_Spatializer" ID="{00C53681-B97C-40CF-B833-585DD6ACE7B3}" WorkUnitID="{54240276-F78B-45D8-BB64-7ABC147B8358}"/>

</Reference>

<Reference Name="Mixer" Platform="PS4" PluginName="SCE Audio3d Object Panner" CompanyID="0" PluginID="149" PluginType="6">

<ObjectRef Name="SCE_Audio3d_Virtual_Bed" ID="{C9D56E06-8082-43C0-BBB4-AFCD8BF4D773}" WorkUnitID="{54240276-F78B-45D8-BB64-7ABC147B8358}"/>

</Reference>