Service Admin unable to unpost journal when approval unit is in Approved Status

Summary:

We have enabled journals, but without journal workflow and unbalanced journals.

We have approval units set up with the separate approve and lock function.

I am a service administrator. When an entity is in the approved approval unit status, I am unable to unpost a journal.

The entities in the approval unit only have owners, I am in the correct group assigned to the top level entity so that I can Lock and Reopen the entity.

Please can I check that this is correct behaviour? Should I expect to be able to unpost a journal as a service admin when the approval status in approved, even though the admin guide says Service admins have write access in this situation.