This sounds like the unofficial versioning scheme of most Rust libraries. That and 2 years old libraries that are at 18.3.5 or something.
Is this a joke or did they just forget to provide a justification for _why_ 0ver should be used?
Probably psychological: major version change equals in people's minds to some marketing event/website announcement, developers/users meeting etc. Which is not how semver was designed. For this kind of event developers should reserve subname, like macOS Mojave, Monterey etc.