The way I see it, you are the one who re-tagged it. The only thing is, it should be spelled "arborists" - without the "u". The tags are used by people to "subscribe" to feeds so that they can see a list of all questions with those tags, plus they get an email when activity occurs on questions with those tags. That's why it helps to usie tags that you know people with certain types of expertise will be watching.
You can write anything you want in the tag space, but knowing what tags are on the feed list of the projects is the key to getting their attention. Some of these are: leaders, team, profiles, improvement, wt_apps, and the names of projects.