"Simple". That's not simple.
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It sounds just the same as every other branched development model.
"Every version is stable" is definitely not "just like every other branched model". Why not just have an increasing number or date as a version number if everything is stable? The major and minor numbers don't make in this way if "everything is stable".
Every release version is stable. That's bog standard in software development. For the kernel, unstable versions are not release versions, they are release candidates.
And they do just have an incremented number, as described in the article. Within each branch, for each release, they just increment the release number (which most people, and semver, call patch). Linux is pretty close to semver post-2.6, but I don't think they limit releases within a minor branch to just bug fixes.
I'm a simple man: bigger numbers mean newer version. And that's enough for me :)