Importing csv file of only email addresses erases name of existing + updated contact, replaces name with email address

I have tested out this bug on the Demo Drupal site on 2.2.2 and confirmed. Here are the steps to reproduce.

1. Upload a CSV file containing new contacts with 3 columns: first name, last name, email address and click any option for duplicate contacts (they are new contacts so it doesn't matter)
2. Assign data to: First Name, Last Name and Email (Main)
3. before Import, add these new contacts to a new group
4. Notice that they are added to a group, and their names show up

1. Now import a .csv file containing only email addresses of these existing contacts
2. Click "update" on the import method for Duplicate Contacts
3. Import the file, assigning these already existing contact emails to a New group
4. The expected behavior IMHO is that the names of these already existing contacts should be retained, and these contacts should now belong to 2 groups
5. Instead these contacts now belong to 2 groups, but the names have been erased and replaced with email address. Their names already existed and should not have been changed or removed

You can find my group "stoob testing group 1" and 2