That’s not a “bug”. We don’t install tools or update tool versions on previous stack versions. The Xcode 8.2 stack will have the same tools & versions as long as it’s available.
You can read more about the stack types and update policy at:
That’s not a typo or failed report. The report simply states that YARN is not installed. We run the same report generator script on every macOS stack, that’s why YARN is listed there, but as you can see in the report it is not installed (and it is expected to not to be installed).