On Page 7 and 8 in the part about linking the XSEDE identity, the document implies that GlobusID will be the user's primary identity, and the screen shots reinforce this impression. In fact, that won't usually be the case. Different users will have different primary identities, and not many people now have GlobusID as their primary. More likely, it will be XSEDE (in which case they don't need to do any linking) or their campus.
I think it would be better if the example used in this doc were someone who has a campus primary identity.