Advanced Block Pick does not save the entities in Boats or Minecarts

Using advanced block pick (ctrl + middle click) on boats, chest boats or minecarts does not save the entities inside them. I would like this to be fixed as my map could use it for summoning "random" entities, and allows for a much more power to map makers

Steps to replicate

1. Get a boat or a minecart

2. Get any mob spawn egg and place it near the boat or minecart

3. Push the mob into the boat

4. Do ctrl + middle click on the boat or minecart

5. Place the item that was added into your inventory

6. Observe that the boat/minecart spawns in with no entity inside it

Expected Results:

The entities get spawned in with the boat/minecart

What actually happens

The boat/minecart spawns it by itself