Using NBT pick block (by default ctrl + middle click) on a decorated pot does not preserve the pot's contents. 

Steps to Reproduce:

1. Be in creative mode.
2. Place a decorated pot on the ground with a comparator facing out of it.
3. Fill the decorated pot with something. The comparator should turn on.
4. Use NBT pick block on the decorated pot.
5. Place the new pot on the ground with a comparator facing out of it, like with the first pot.
6. Observe that the comparator was not activated, thereby indicating that the pot's contents were deleted.
7. If the gamerule doTileDrops is set to true, then one can also confirm that the pot's contents were deleted by breaking the pot.