I don't think it's about restraint, it's about (as you said) the severe cases and anaphylaxis on contact, not even ingestion. I had a boy in soccer carpool for a few years who had an extremely severe peanut allergy, and I was always freaking out that there might be an old pbj sammie under one of the seats or something ... the kids ate tons of pbj's when they were younger; it was a staple for breakfast and afternoon snack.
Regarding the PB&Js, you're right that due to the life-threatening allergic reactions that some kids can have, they're an issue.
As a private, low-cost option for ski nutrition, they're actually a very good one to consider, though, assuming you and your group don't have the severe allergy issue. Basically an affordable version of an energy bar that also can survive (sort of) in a jacket pocket or pack over a range of temperatures. While there's nothing to suggest a PB&J will help someone develop motor skills better than other options, they are actually good pre, mid and post workout foods for endurance athletes. Because a full day of skiing does have a significant endurance component, they're a good option for people to keep in mind for ski day nutrition. And, particularly good since kids seem to like them most of the time.
The wrinkle of substituting sliced bananas for the jelly is a good option to remember, particularly if the sandwich is going to get a lot of jacket or pack abuse.