“version numbers never change” (which is what stable means in Debian Stable).
My interpretation of stable isn’t just versions not changing, only that the bugs are known and newer ones aren’t easily introduced, i.e. the state of the system is known. While rolling releases are fantastic for end users and to obtain the latest software, sometimes a particular bug or change will modify a user’s workflow.
What’s the main difference? From the link it seems to be a cryptocurrency with the same payment features.