Tall flowers sometimes spawn in village farms

On seed : 6423931808280740681 at coordinates 299 80.00 -197 lilac flowers sometimes spawn in a village farm (on logs and water blocks). When I left the game and came back they disappeared. They also didn't spawn when I created a new world with the same seed and used /tp to get to the village, but when I made a third world and came there without using any commands they spawned.