Similar to TMS, WS shouldn't write unconfirmed segments to the TM at all. Linguists leave segments unconfirmed, generally, in order to keep them from the TM for a variety of different reasons including: one-time project specific instructions, one-time ICR or other third party feedback that shouldn't be implemented in the future, etc.
Suggestion: Create a setting to let organizations choose if unconfirmed segments should be written to the TM or not.