I view “natural ingredients” as a marketing ploy. Nature is full of toxins, and most tanned leather has been exposed to unnatural chemical extremes to break down collagen and strip out other stuff. So I’m looking for quality ingredients, whether synthetic or natural. Fiebings Aussie conditioner seems waxy to me but doesn’t darken leather, similar to Bick 4, whereas Blackrock Leather N’ Rich is waxy and consistently darkens leather. I assumed it was an oil that darkened the leather.
I wonder if the petroleum distillate you mentioned is the same one in neatsfoot compound. In the Encyclopedia of Saddle Making the Stohlmans note they used a lot of neatsfoot compound to good effect but recognize that pure neatsfoot oil is a superior product.