The recipe, as given, uses no spices, just the meat and rendered fat.
I would be cautious of adding any spices unless there were a way to sterilize them. I confess I don't know of away to sterilize leaves, seed or roots that also keeps them dry. Perhaps radiation treatment... Got an x-ray source or UV lights? Not an item on my BOB list.
Perhaps spices could be boiled and then dehydrated, with caution taken to keep them sterile during the process. Some loss of flavor might occur (or a lot, depending).
Spices should, at a minimum, be absolutely dry to avoid introducing any water into the container, which offers a path for bacteria or mold. That means no fresh spice leaves.
The primary goal in potting is to seal the meat away from any oxygen.
Since the meat, as described in the article, is NOT eaten straight out of the pot, spices can be added you're when ready to use some of the meat in a recipe.
But, yes, if you're hungry, you could eat the meat/fat mix, but... Similar to Pemmican in this case. Sticks to the roof of your mouth.