hopper minecarts are picking up items fine, but they are not putting items into block gui's.

i was just derping around with the new hopper minecarts and i put a track on a dropper and then a hopper minecart and put some items in, but i had noticed that the items weren't transfering to the dropper so i had tried it with other blocks like the furnace (with coal) and dispenser.

Steps to Reproduce:
1. put a dispenser, dropper,or furnace down.
2. get any kind of tracks and shift place the track on any of those 3 blocks.
3. put a minecart with hopper on the track.
4. throw or place items in the hopper minecart's gui.
5. notice that there are no items going to the gui of the block under the hopper minecart.