Import Phone using update overwrites wrong data

When importing contact records with phone fields and using the update option, CiviCRM does not update the correct phone_type, but replaces phone fields with the new data regardless of phone type selected, and also designates the first phone field in the imported data as the primary phone.

Replicated on 2.0 Sandbox. The 2.1 Sandbox update option appears broken – attempts to import using update created new records.

To replicate the problem:

1) Note that the John Doe record in 2.0 Sandbox has a "Pager" phone value.
2) Import the attached file with "Update" option, and using the "Phone Import - Update" mapping.

Expected behavior:
1) Pager phone is retained.
2) Phone/Mobile/Fax data is imported.
3) Contact results in four phone values.

Actual behavior:
1) Pager phone is overwritten by the three imported phone type values
2) Contact results in three phone values, the first of which is designated the primary phone.

The behavior is identical of the "Fill" option is selected.

This is problematic – in my case, I have a complete set of new phone numbers that need to be imported as a new phone type, after the initial import has taken place. I'm unable to do that without risking a complete overwriting of the data. (I have a workaround, but this is a data loss issue for users.)