See flutter/packages#2987 (comment) for example context. The tooling shouldn't allow a change of version B to version A<B if version B is published already. It should instead fail with an error message saying that if it's a revert it should instead:

• revert all the code changes
• bump the version to B+1
• consider retracting version B, and if that's going to be done, adding a note to the changelog entry for version B in the B+1 update