The SDK moved through three releases in steady increments. Version 2.9.0 landed in late February, followed by a patch release 2.9.1 in early March, and then 2.10.0 shipped in April. The minor version bump suggests feature additions alongside the patch work, though the release notes point to the full changelogs for specifics.
The OpenAI .NET SDK shipped a single patch release on March 2nd with targeted fixes documented in the changelog.