When you hit a tall grass block from the bottom part, the peony flower block will flash instead of the tall grass.

Normally one should expect the same block they are breaking to show up,

But instead the peony flower flashes instead.

All you have to do to reproduce it is hit the tall grass block from the bottom section, and you will see it.

I recorded a video of the glitch and have attached it. It's in not the best quality because I had to make it not exceed 10MB.