I have heard this piece of information so many times before, I am curious where it originates from? Cause if these snakes got stressed so easily in an large environment, how do they survive in the wild? I have never seen/had issues with small snakes in large enclosures as long as you provide enough cover for that species. As a purely biological stand point, when snakes are young they are at their most risk of being predated in the wild, so therefore they will want to limit their exposure to predators. An example I have seen are baby snakes living within a large gorse, and the fact they would use all the gorse and not just a small area should suggest that when given the opportunity use as much space as needed, as long as it still gives them protection?
The perfect example of an urban myth.