The short answer is no. A snake will not die because you feed it in its enclosure. The person that told you this is the idiot, not you. As stated above, the only potential issue could be the ingestion of a very large piece of substrate that the snake's digestive tract cannot handle. There is an episode of ViperKeeper where he removes a very large piece of substrate from a young snake's stomach if you are interested in an extreme case.
Wow... Delena even started the post with the same sentence. LOL.