gknoy parent
If they rely on the client to determine when things are deleted from their service, they're doing something wrong. Never trust the client software! The only thing a rogue client should be able to do is surreptitiously send a copy of your pictures Somewhere Else (for storage). All the pictures sent to Snapchat should get deleted on schedule, regardless of who or what sent the pictures.
If they allow the client to display the image, they allow the client to do anything with the image. Of course they stop serving images on a particular schedule. (I sort of doubt they stick with that same schedule in deleting from their central storage, but whatever.) Since Snaphax is completely client-side, however, their server policies are irrelevant.