Nether wart brought into existence with the /blockdata command can't be used to brew awkward potions.

1. Put down a hopper and a command block on top of it.
2. Plug in the command /blockdata ~ ~-1 ~ {Items:[

{id:"nether_wart"}

]}
3. Try brewing water bottles into awkward potions using this particular nether wart. Observe that the items just sit there, and do not brew. Also this particular nether wart will not stack with wart brought into existence by other means.