The vegetable oils are saturated fats, which will mix with the peanut oil, but solidify at room temperature. That and the sugar are doing the leg work on keeping the peanut butter from separating. So yeah, saturated fats and sugar are unhealthy additives specifically for preserving the peanut butter. What exactly is your definition of a preservative?

Everything is palm oil these days

There is definitely salt in my aldi peanut butter, and a lot of sugar, I can tell just by taste without checking the label.

You can get some brands which have a pinch of salt added, but in my experience, most brands don't...