When the block that a grass/flower block is placed on is moved by a piston, the flower does not get broken and instead stays where it is. This is demonstrated in this video: https://youtu.be/NvZ8J05w3iU?t=6m
Linked issues
Comments 2
Duplicate of MC-123311
I added the additional information to the original ticket.
Was able to re-creare this in Minecraft 18w08b