The assumption here is that subliminals act to tell your subconscious what it could not figure out on its own, or that the subliminal was the root cause of experiencing a communication with your intuition that you hadn’t experienced before.
Lots of subliminals have suggestions in common, ie the primer, as well as objectives. One of the objectives of Ascension is “Develop and Embrace a physically and emotionally healthy lifestyle.” I’d say that’s where the motivation came from to bring the intuition about the salt to you. But knowing what is best for you specifically? That’s something only your greater being (a term I’ll use in place of subconscious) can do, not a subliminal. If there were specific dietary suggestions built in to the subs, that could cause all sorts of medical issues.
That’s where the design principles of Zero Point come into play, in opening the greater being to ask the question of what the new desired state or objective means to you, or the steps to get there, because you’re at the center. Same as if Alchemist etc made specific religious suggestions it could be problematic.
But as to why salt, I don’t think we give ourselves enough credit sometimes for knowing intuitively what is right for us. You just got the motivation/desire to make your lifestyle healthier from the sub, and then you figured it out from there.