Rows not deleted from content_field_xxx table, when node is deleted

When I delete a node that contains a multi-valued emfield, the emfield database entries are not deleted. Rather than deleting the relevant rows from content_field_xxx, it seems that emfield is instead re-setting the field values for these rows to NULL.

Specifically, here is what I did:
A. Create nodetype with a multi-valued emfield, "myemfield"
B. Create node and populate two of the emfields with youtube url's.
C. Look at database table "content_field_myemfield".
It contained one row for each of the two populated emfield. Each row is populated with the url data.
D. Delete the node
E. Look again at database table "content_field_myemfield".
It still contained one row for each of the two populated emfield. Instead of deleting the relevant rows, emfield replaced the url data with NULL data.