What is the difference between tail_fetish and tail_play? The wiki page for tail_fetish doesn't really specify what should be included that would not be covered by tail_play and the amount of posts that are tagged tail_fetish but not tail_play is currently 69 out of over 9k.

Am I missing something here or is tail_fetish just a redundant tag?

the I believe that the *_play tags are for when the body part is directly involved in a sex act or being directly interacted with in a sexual matter (so, essentially the equivalent of anal, vaginal, penile, oral). *_fetish is, in addition to *_play, also used when a bodypart is used as a thing of sexual desire.

the difference is most prominent with foot_fetish vs. foot_play, mostly just the larger sample size.

It looks like tail_play is expressly for sex or masturbation involving the tail (according to the wiki, if there's no sex or masturbation, tail_play shouldn't be used), while tail_fetish is for more general sexual behavior involving a tail (sexualizing the tail regardless of there being any sex or masturbation). I wouldn't be surprised if they're both being overtagged to the point of being indistinguishable, though.