> For example, I used to report the trans slur of the "t" word and Facebook would remove the content. Now, when I report it, the comment stays posted.

Isn't that also a slang term for a transmission? An automated rule for that that would probably result in far too many false positives: merriam-webster.com has the transmission sense as the first meaning, and has collected many very recent usages from auto magazines: https://www.merriam-webster.com/dictionary/tranny.