When I look at the list of the newly created tags on Mathematics Stack Exchange, the tag triangle is listed there.
This seems a bit unusual, because this tag is a synonym of the tag triangles and the synonym has been created already in March 2019 - both according to the list of synonyms and SEDE. There are also some posts here on meta - again from 2019 - which mention this tag synonym: Why were all the "triangles" bronze tag badges "Awarded Mar 25 at 4:00"?, Tag triangle and triangles and the answer related to this tag in Tag management 2019.
So how can this be a new tag - when the data about the tag synonym says that this tag existed already in 2019?
Here is a screenshot showing how the list of the new tags is shown to me:
