One theory is that snakes are able to make some sort of judgement about whether or not their food has the potential of harming them, and they may not bother to waste the energy on coiling if it doesn't. I don't know how true this is, but I've observed nothing to contradict it. I've seen lots of baby mice get swallowed live, but each and every time I've fed an adult mouse, it gets "killed" by the snake even if it was already dead before the snake ever saw it.
Another possibility, when it comes to baby corns, is that whatever things are available to a baby corn in the wild are things that aren't dangerous to them, so they evolved to not develop a very strong strike & coil response until they are more mature, rather than it being something they really evaluate at each meal.
I think a lot of people who object to mice in the freezer are concerned about the germs they imagine will crawl from the mousicles and get in the ice cream. Oddly, these same people have no concern about the germs that might crawl from the raw chicken and get in the ice cream. It makes no sense, but you have to keep your family happy, so some things that help are multiple layers of (mostly) germ secure wrapping, including at least one opaque layer so no one will have to see the mice. Also agree on a place, preferably on the bottom shelf so people can't imagine mouse germs falling onto the people food, that is designated for the mousicles. I'm not sure how much any of these things actually do to reduce the possibility of mouse germs contaminating the people food, but it definitely seems to make people feel better about it.