As you probably saw in the warning bar located at the link you provided, the APIs are currently in an 'alpha' state. Part of that reason for that is because we do not yet have all of the automation around keeping documentation in sync with the releases as of yet as you pointed out; although it is being developed as we speak. While the APIs are production stable and used by our own UI, we wanted to allow earlier access directly to the APIs in order to get feedback but did not want to compromise on our commitment to quality and community what we'd consider sufficient support and backwards compatibility mechanisms in-place to officially version them publically.
In the meantime the release notes for Launch as a product can be found in the Help Documentation: https://docs.adobelaunch.com/getting-started/release-notes and may provide some info about API specific notes, but no gauntentees at this time. Again, we plan to provide more API specific release notes in the future.