Good catch! This was from this import project:

osm.wiki/Import/Catalogue/Australia_NSW_Property_and_Address_Import

Most information and the full history of uploaded and reviewed address files is in the GitLab repository:

https://gitlab.com/dionmoult/osm-nsw-address-import

My best guess as to what happened here is that the script fetched points within a bounding box which included the suburb. It was then supposed to remove points which were not from the suburb in question. In this case, it would have removed points which are not from Killara. However, I'm guessing there was (or is) a bug which prevented it from removing points from East Killara. (These should have been removed and added in a separate changeset).

The second issue is that the LPI property API returns the address as a single field '10 Example Street Suburb'. To split this into the format required for OSM, the script removes the right-hand side of the address matching the suburb we are supposed to be uploading. In this case, it removes 'Killara' from the right-hand side of the address. However, because it failed to exclude the 'East Killara' addresses earlier, it just removes 'Killara' from the end, and leaves '10 Example Street East' as the address.

Sorry for not catching this in review.

I've changed it here:
changeset/75049968

I see your point.

Would you accept building=office instead?

I've fixed it here:
changeset/74982346

Reading the wiki for admin_level gave me the impression that it was only for boundaries. Reading it again carefully I see that you are correct. I'll add the tag back.