Unable to Find OculusXRPlugin When Plugin Not Enabled?

I am receiving an error "Unable to find OculusXRPlugin" even when I do not have the Oculus XR Plug-in Provider enabled in the XR Plugin-in Management Settings.

Why is it attempting to find/load this plugin when the provider isn't enabled? 

I have a single code base that supports three different VR headsets and a build script that enables the proper provider. This works for 2 of the providers but now having added a third, this 3rd provider doesn't work properly unless I completely uninstall the Oculus XR Plugin package.

I would prefer to leave all of the providers in the code based and selectively enable as needed.