Right now, "kind" only has 26 results as of the time of writing (September 24, 2021), and the help page doesn't have any information regarding it. It also seems quite abstract: to me, it implies that someone is acting kindly to another? But that doesn't really translate well into concrete search results.
So, as it stands, it seems like it's somewhat a waste of a tag that would provide far greater utility as being an alias for "type", since the two are closely synonymous.
Footnote: I did a double check, and we also already have a "kindness" tag, making the actual purpose of the "kind" tag quite obscure in addition to all of the above. It also has 25 results, meaning that the two tags "kind" and "kindness" are likely used for the same thing.