When a Shulker Box is placed against the bottom block of tall grass, the Shulker Box will be placed upside down.

Shulker boxes placed against grass or other similar plants can also behave in other odd ways. Placing a Shulker Box on the side of normal-height grass will cause the Shulker Box to replace the grass and be facing sideways.

When other blocks like logs and pistons are placed against grass, they break the grass first and are then placed as if the grass was not there. Shulker Boxes should also behave this way.