You're wrong. NFE mons follow the same rules for rising and dropping as other mons. If Delibird or Golbat rose from untiered/NFE/ZU to NU and then drops the next month, it drops to PU if it were also to rise to PU in the month it rose to NU, while it drops back to untiered/NFE/ZU if it did not get enough usage in PU.Yes ZU is adressed by many, but Marty didn't adress it in his quickdrops, so no quickdrops went to ZU. Furthermore, it's a NFE Pokémon. If something like Delibird rose up, it would quickdrop down again, but Golbat isn't tiered like the other mons, so it will be PU first then ZU, or rather NFE, again. Same goes for Clefairy. Furthermore, ZU is technically Untiered, so mons don't drop to ZU, they become Untiered. I hope that in the near future, it will be become a new tier, but for now it's not.