My guess is more simply that "tardigrade" contains the substring "tard", which is sometimes used as short for "retard" in their state of the art regexp filter.

Their filter is probably like /iran|tard|cuban|.../i (see also: https://www.insidehook.com/daily_brief/news-opinion/paypal-w... and https://news.ycombinator.com/item?id=24359821)