This is expected, and one of the reasons why the version numbers differ between Roman and Italic.
Work on Italics started after the first versions of the Romans had been released, you can read more about the development of the Italics here: https://blog.typekit.com/2018/08/16/source-serif-italics/
That said, work on achieving feature parity between Romans and Italics is in progress, as seen in the greek-italic branch.
This is expected, and one of the reasons why the version numbers differ between Roman and Italic. Work on Italics started after the first versions of the Romans had been released, you can read more about the development of the Italics here: https://blog.typekit.com/2018/08/16/source-serif-italics/
That said, work on achieving feature parity between Romans and Italics is in progress, as seen in the
greek-italic
branch.