Who says?
Anyway, at this point we're debating semantics; all it boils down to is that some people on this site don't like the word fetish; it drums up connotations of creepy and weird (though having seen some of the topics on these boards, I sometimes think it's an entirely appropritate label 😎)
I rarely refer to my love of tickling as a fetish; I have done, and still do occasionally. But it depends on who I'm talking to, and whether they'll take the word fetish in a bad way or not (most often, they don't). I might call it a kink, or interest, or whatever. It doesn't matter what I call it, because the bottom line is that it turns me on. That is what people are going to take issue with, if they take issue at all that is.
Besides, tickling partialism is such a shit name for a kink.