When using bonemeal in singleplayer you may notice that sometimes flowers spawn and they disappear
The same applies for crops, they grow, and then change state.

That's because the server generates a random number (to generate flowers, to make crops grow, etc.) and the client does that too. The client doesn't listen the server so does what it generated but as soon as the server sends an update for the block, the flower disappear or the crop changes growth state.