Security is an umbrella term. You can't just assume that secure things are private--you have to make the determination in context with whatever kind of thing it is.
The primary goals of a system like radicle are:
- spread the word
- don't let anybody alter it
If you ask if it's secure, you should assume you'll get an answer related to those purposes.
If you got a sunburn while standing in line for a water slide, you wouldn't say that the slide is unsafe, even though being burned is a hell of a departure from "safety". You'd have to be a little more specific.