Every version is stable in linux means no version breaks userspace. Semver's major version literally breaks the contract. It's what it's for.

And even if we literally meant stable as in "this is expected to work", no, that is nowhere near normal in my experience. There are countless projects and companies with "test in production" mentalities. Then there are distros like Ubuntu and nixos that always have an unstable and/or a testing release, which is by definition not stable.

So, no, every version is stable is definitely not the norm in my experience.