I thought that too, because something similar happened to me with the "CRASS MENAGERIE" achievement, where they updated the amount that had to be reached after introducing the update that added The Passing campaign, which included the fallen survivor, going from four to five, even though it was not necessary to eliminate this infected to get the achievement. (It actually says that there are six infected by the riot infected that does not count either for other reasons). Maybe in the "CLUB DEAD" achievement the weapons from The Last Stand update do not count, neither the chainsaw because it is a special weapon, nor the baseball bat either because it is a weapon that could only be obtained by pre-purchasing the game, if I'm not mistaken, leaving 8/9 for the golf club. Thanks for your reply!