Should vendored cookbooks always be added to the cookbook_path?

My current SOP with ChefSpec is to test my cookbook completely in isolation from any others (including any wrappers in test/cookbooks), so it came as a surprise that, post-1.2, overriding the cookbook_path still results in vendored paths being added.

Should it be possible to specify an exact cookbook_path that ChefSpec won't add anything to, or am I an unusual use case here? I have a workaround already but, in my mind, if I'm specifying a cookbook_path to the ChefRunner, I'd expect that to override any defaults. Maybe it's just me.