Snakes are stressed in large cages?

Much like "you must feed in a separate enclosure or your snake will associate you with food," and "if your hot spot is too hot your corn will get burned," another instance of Internet regurgitation I hear tossed around a lot is "Put your babies in a shoebox, anything bigger will make them feel stressed!" Hogwash! They naturally hatch outdoors. Poor things must be losing their mind in that big of an enclosure!

I do use shoe boxes for my babies, and used to use much smaller tubs, for a number of reasons. But never has one of the reasons been that the snakes themselves would be stressed with more room. Off the top of my head, here are the reasons to keep babies in small containers:
1) Space. Corns make lots of babies, and I have lots of corns. Space is at a premium.
2) Feeding. It is simply easier to get the snake in close proximity to their food in a small space. It often takes being put with food in tiny deli cups for some brand new babies to figure it out.
3) Cleaning. Small tubs are easier to clean than big ones.
4) Keeping track. Sheds, defecations, uneaten meals, and the rare regurge might not be found in a 100 gallon aquarium, I'll spot them right away in a shoe box.
5) Finding the snake!
6) Heating. It is easier to heat small areas than large ones.
7) They simply don't need more room than a shoe box until they grow to 30-40 grams or so, at which point I move them to a 15 quart tub.

Give your babies a clean, escape-proof enclosure of the proper temperature, with fresh clean water and feed them appropriately sized mice. With the exception of the rare one that wasn't meant to make it, that is all they need to thrive. Avoid humidity extremes, as well as hides and objects they can hurt themselves on or get stuck in. In my opinion, small enclosures have nothing but upside for new babies. But lack of "stress" that is supposed to occur in a large enclosure isn't one that I buy.

I have only had one snake react badly to being moved to a larger enclosure, our female Mandarin ratsnake that had been in a 10 gallon tank for almost 2 years, from a tiny 13 gram hatchling. We moved her up to a 20L when she was getting quite long and figured she'd pretty much outgrown it. She wouldn't settle down, was constantly striking the cage and rattling her tail over every little bit of movement near the cage and refused to eat, despite enough hides and clutter in the tank. We eventually had to cover the whole tank with a towel for about 6 months, gradually lifting it up on the front and sides, until she was uncovered again and she finally adjusted to it.
That was in a glass tank though, she might not have had a problem moving into a larger opaque tub or something, though she had been doing fine in a smaller glass tank.

So I'd say it is possible it could cause stress in a few rare individuals but is not as common as lots of people think, for sure.

I would chalk that up to change in environment. I have had snakes suddenly get high strung from moving them to a new enclosure, just had a corn do it this year -in this case, moved to a different rack of roughly the same 15 qt size. For sure, many get used to what they consider "home." I doubt had yours been put in a 20L to start with, if she'd have been a wreck sheerly because of the cage size. Had that same snake been hatched in the wild, I don't believe for a minute it would have felt stressed by openness of the great outdoors. Stress isn't easily measurable, so it's hard to say when a snake is truly "stressed," unless they are flat out freaking, like you describe, or go off feed. I've had so many hognose fast after moving them, that I am paranoid to even do it anymore. Makes no sense. I can clean the tub, add new bedding and water bowl, and they are fine. But move them to a different tub in a different rack, and they go off feed. Temps, substrate, hides, everything (even tub size) is the same, but it can take a month to get them to feed again. This doesn't seem to happen with corns often, but they are less finicky to begin with.

I've put babies straight into a 20L- they do fine. Just hard to find!