waste_road is correct and you are wrong. the point they are making makes complete sense.

yes obviously pinky has a "higher" drop rate; getting the pinky to spawn is the what makes it equivalent. you can kill a hundred slimes before you even see your first pinky. the rarity of being granted the chance to hit the random numerical value of pinky's drop rate of the slime staff is what makes it equivalent. almost every single start of the game there are slimes surrounding you, therefore there are chances for the staff to drop all around you. you don't get the chance to get the "better" drop rate from pinky without already hitting the random numerical value that causes the pinky to spawn.