Membership – User Registration Question

I’m seeing something weird with the Membership plugin.

When a user tries to register on a subsite with the Membership plugin installed, if that user already exists at the top level multi-site, the registration fails – “That email address is already taken sorry”

It seems to me that if the user already exists on the multi-site then they should be assigned to the membership site rather than having the registration fail.

They way is currently works, if someone is a customer on our blog network, they cannot sign up to another customers membership site.

Make sense?