There are no new features nor behavior changes in CWL v1.2.1 as compared to CWL v1.2.0. v1.2.1 fixes only typos, adds clarifications, and adds additional conformance tests. Some changes to the schema defining CWL are to aid the auto-generation of libraries for the reading and writing of CWL documents.
https://deploy-preview-115--cwl-v1-2-dev.netlify.app/workflow#Changelog_for_v1.2.1
https://deploy-preview-115--cwl-v1-2-dev.netlify.app/commandlinetool#Changelog_for_v1.2.1
Final feedback to https://github.com/common-workflow-language/cwl-v1.2/pull/115
The CWL Technical Team is voting now; which will be followed by the CWL Leadership Team voting and presumed ratification.