Here's the thing. Releasing animals into the wild will probably result in their deaths anyways. Since it's winter, the snails would probably freeze to death. They probably wouldn't starve but there's also a good chance that something eats them. So it's not that they wouldn't die. It's that it would be out of sight. So someone can fool themselves into thinking they weren't responsible for it dying. But freezing or starving isn't a particularly humane way to die. Releasing animals into the wild is irresponsible and it's taking the easy way out. And of course, there's an even worse case scenario of them becoming an invasive species. Which would result in other animals dying.