I doubt this is your first time experiencing this phenomenon (partly because I’ve covered it before), but in case it is:
Adding the word “very” implies LESS of something. My classic example is “We have a full plane” means something specific… but “We have a very full plane” leaves you with hope that the adjacent seat will be empty. Very full is less full than full.
Very quiet is less quiet than quiet. Very possible is less possible than possible.
But it only recently occurred to me that the same feels true of “Soon”. It’s not as black and white as the previous examples. But consider your feels: “The plane will be taking off soon” gives you a little bit of hope. “The plane will be taking off very soon” means someone is still working down there with a wrench waiting for a part to arrive from Columbus.
I’m very interested in your thoughts on this. 😉
I don't usually chime in here, but I thought I'd just pop in to register my interest in, but disagreement with, your claims. When I say that a suitcase is full, I usually mean that something occupies every part of it; but if I say that a suitcase is very full, then I mean that it is essentially stuffed to its limit (& I would use those words similarly about my stomach after a meal). So, for me, "very full" is always more, not less, full than just "full." A library reading room or train car or automobile engine that is very quiet, in my ordinary usage, is certainly quieter than one that is merely quiet. I suppose you may really be commenting not on the actual meaning of "very" in those cases but on what it leads you to imagine about the circumstances under which it's uttered. Personally, I have less hope of an empty seat beside me when the flight attendant announces a "very full"—rather than simply a "full"—flight. But maybe I take things too literally. My own usage of "very" alongside "soon" aligns with my usage of it alongside "full" (i.e. always as an intensifier), but I won't deny that if I heard it used in the example you offer, I might come to a similar conclusion.
Here's another one: "So perfect" is less perfect than "perfect".