This is not the case for skiing at least. My young kids (who are are not exceptional) have been skiing for the last few years. They rarely fall. It might happen once during the day or not at all. And they didn't fall much on their first few days of ski either. (I also don't remember falling much when learning how to ski as a kid.)
In fact I'd say the same for biking. There is a myth that you have to fall to learn how to bike. Yes, you might fall once or twice and learn a lesson but that's it. Most of the learning process doesn't require actually falling to the ground.
Now it could be different for snowboarding but I don't have experience with that. It could also be a little different for adults learning how to ski but even there I'd think it can be done quite safely.
Of course I agree that for adults (and especially older adults) falls will have worse outcomes than for kids on average.