Ignore this, see
Double-size plants (the ones that take up 2 blocks), when mined from the top always produce Sunflower particles (curiously this is damage value 0 for double-size plants), and tall grass doesn't drop stuff (unchecked) when mined from the top.
When mined from the bottom, the top part of the plant turns into a Peony (curiously, the last damage value for double-size plants, this was reported in
MC-53439) for a split second then goes away. If tall grass is mined from the bottom, it can drop itself without using shears, or drop a textureless block that turns into seeds in the inventory (possibly the entity dropping as a block instead of an item).
This could crash the game randomly.
MC-29559 2 block tall grass/fern does not produce seeds when broken
MC-53439 The top block of a two-block plant temporarily becomes a peony/sunflower upon placing a block in the bottom
MC-59258 Breaking grass or tall grass can drop seeds with a missing texture
MC-59327 Breaking bottom block / replacing top block of double-tall plants yields double-tall plant item