I think it's relatively intuitive for lay users that the links are secret. If you give someone the link, they get the file. What's not obvious about that?
If anything it's probably harder to understand for a somewhat semi-technical person who probably has started to think about encryption and so on but hasn't got far enough to spot that oh - the secret key is in the URL itself as an anchor and so the URL is the secret.
Computer Security is often nicer here than real world physical security, because we are often able to make the extreme cases so implausible as to be irrelevant, enabling intuitive statements to be true in practice rather than subject to endless caveats.
For example a lay person sees a padlock and they imagine that it cannot be opened except with the padlock key. And this is untrue in lots of ways - so a more technical person may think of some of them, and identify that this particular brand of padlock defends against those well, but not realise that other problems are undefended.
So this means the truth about the padlock has to be more nuanced and relative. Breaking the lock open with tools is "difficult". Picking the lock "cannot easily be done in under a minute". But lay people don't like nuanced, relative statements. It sounds a lot like this padlock won't really stop someone stealing my bike! That's because it won't.
But in computer security we often can make these cases irrelevant in practice. What if someone just tries all the key values for this AES encryption? That's fine, there are so many that even if they could try as many as there are grains of sand in the world, every second, the sun would burn out long before they had a meaningful chance of guessing the right one.