But someone will have to go back and clean up later. For original cataloging there will be no change in timeliness. For copy cataloging, all the alternatives will require more work on our part, which will have a small impact on the timeliness of providing cataloging. Practice shouldn't vary simply because different systems handle information differently. So yes, the responsibility falls on the catalogers, but it should be a simple rule to follow.
Some folks have a considerably greater relative investment in series than others.
That does not keep us from properly including alt titles in our OCLC inputs and 4XX's in our OCLC input authority records even though we strip these out for the local system. If the benefit outweighs the cost then the change was made retrospectively. Let's not get hung up on a perfectionist scenario where the most unusual cases might be problematic to parse in any way. Again, the whole idea behind cooperative programs is that I can accept what someone else has done instead of recreating it myself. If I have to double check everything, it defeats the purpose of working cooperatively.