Interestingly, being `0.y.z` as a major released version (e.g. not in development or a release candidate) does seem to break semver[1], but I do realize it's more of a guideline and no one really cares:
> Major version X (X.y.z | X > 0) MUST be incremented if any backwards incompatible changes are introduced to the public API. It MAY also include minor and patch level changes. Patch and minor versions MUST be reset to 0 when major version is incremented.