I think I got it. I set the Tag Type to not allow multiple values and used the UPDATE in the csv.
Yes that is the answer. (do not allow multiple values)
Be aware that tags to not 'unset'. Meaning when the config item is removed, the tag that has already been set will not unset.
We 'fixed' this by occasionally (twice in 5 years) clearing all flags of the offending type, and re ran the tag rule.
This unset process is useful when you have a multiple value tag that has gotten out of hand. Unset all of that tag type, then let the tag rules run.