Theoretically, they could be included, but it’s incredibly unlikely that rations would contain any type of additional seasoning for a couple reasons.
As a preface, this answer applies to the standard D&D setting: a medieval fantasy world. If the setting of your game is different, say a steampunk setting, or a futuristic space odyssey, this doesn’t apply.
First, it’s simply logistically unfeasible. For people today, a packet of salt and pepper packed in with their disposable plastic cutlery is a common convenience. We have mechanized factories that can mass-produce the paper packets that we store them in, and have a cheap means of moving them from place to place for distribution. In the medieval setting that’s like the standard for most D&D games, production of such convenience items is unlikely, due to simply lacking the technology required to do so. They simply wouldn’t have the resources to mass-produce packets to put with every potion of rations regardless of the material they were made of.
Second, extra salt on the side would be unnecessary. Rations are intended to stay good for a long time, weeks or even months, in a place where refrigeration is virtually non-existent save for the incredibly wealthy who can afford a powerful mage to create a magical ice box, or powerful mages who can do so themselves. This means the rations need to be preserved in some other manner, and resistant to rot and mold. Since salting was the primary (and in most places, often the only) means of preservation, most of the items that would go into a ration are already heavily salted. The cheese and tack might be of a particularly hard type that would be resistant to growing mold, but you generally wouldn’t add salt to those. The nuts would likely be roasted, and probably already salted for flavor anyways. Any kind of meat by necessity is already cured, salted, and smoked, because it simply won’t last otherwise.