Profile with only email field sets display name of existing user to email address

Using a profile with only an email field sets display name of existing user to email address

reproduced on demo, not logged in, go to:

http://demo.civicrm.org/drupal/civicrm/profile/edit&gid=2

fill in the email of an existing contact ( neila@magma.ca )

The contact (Neil Adair) will display the email address, the first/last name display will revert on edit/save